Exam Elementary Physics Chapter 28 Part 1

ch 28 What is reflection? the return of light rays from a surface What is refraction? the bending of an oblique ray of light when it passes from one transparent medium to another When a piece of regular paper is illuminated by white light, the paper appears white. What does this reveal about the electrons? That the electrons re-emit all the visible frequencies; very little absorption occurs. What is Fermat's principle of least time? Light takes the path that requires the least time when it goes from one place to another. What is the law of reflection? The angle of incidence equals the angle of reflection. What is diffuse reflection? Reflection in irregular directions from an irregular surface What is the critical angle? The minimum angle of incidence inside a medium at which a light ray is totally reflected. What is total internal reflection? The total reflection of light traveling within a denser medium when it strikes the boundary with a less dense medium at an angle greater than the critical angle. What is a converging lens? A lens that is thicker in the middle than at the edges and that refracts parallel rays to a focus. What is a diverging lens? A lens that is thinner in the middle than at the edges, causing parallel rays to diverge as if from a point. What is a virtual image? An image formed by light rays that do not converge at the location of the image. What is a real image? An image formed by light rays that converge at the location of the image. A real image, unlike a virtual image, can be displayed on a screen. What is aberration? Distortion in an image produced by a lens, which to some degree is present in all optical systems. What evidence can you cite to support the claim that the frequency of light does not change upon reflection? The color of an image is identical to the color of the object forming the image. When you look at yourself in a mirror, the color of your eyes doesn't change. The fact that the color is the same is evidence that the frequency of light doesn't change upon reflection. If you wish to take a picture of your image while standing 5 m in front of a plane mirror, for what distance should you set your camera to provide the sharpest focus? Set your camera for 10 m; the situation is equivalent to standing 5 m in front of an open window and viewing you twin standing 5 m beyond the window. Distinguish between reflection and refraction. When light is returned into the medium from which it came, we call it reflection, while refraction is when light crosses from one transparent material into another. How does incident light that falls on an object affect the motion of electrons in the atoms of the object? The electrons vibrate more energetically in response to the oscillating electric fields of the light. What do the electrons affected by illumination do when they are made to vibrate with greater energy? They re-emit the light that falls on them. What is Fermat's principle of least time? Light will always travel the path from one point to another that requires the shortest amount of time. Relative to the distance of an object in front of a plane mirror, how far behind the mirror is the image? The image is as far behind the mirror as the object is in front of the mirror. What fraction of the light shining straight at a piece of clear glass is reflected from the first surface? only about 4% Can a surface be polished for some waves and not others? Yes; a surface may be polished for radiation of a long wavelength but not polished for light of a short wavelength. How does the angle at which a ray of light strikes a plane of window glass compare with the angle at which it passes out the other side? The angles are the same. Is a mirage the result of reflection or refraction? Refraction. What is the relationship between refraction and changes in the speed of light in a material? ... How does incident light that falls on an object affect the motion of electrons in the atoms of the object? Incident light makes the electrons oscillate. The electrons then emit light or absorb the light and convert it to heat. What do the electrons affected by illumination do when they are made to vibrate with greater energy? They reemit more light or collide with neighbors, thereby converting light energy to more internal energy. What is Fermat's principle of least time? Light takes the quickest path in going from one place to another. Cite the law of reflection. The angle of incidence equals the angle of reflection. Relative to the distance of an object in front of a plane (flat) mirror, how far behind the mirror is the image? The virtual image is the same distance behind the plane mirror as the object is in front of it. The virtual image and object will have the same size. What fraction of the light shining straight at a piece of clear glass is reflected from the first surface? about 4% is reflected from each surface, for normal incidence (light perpendicular to the surface). On clean polished silver surfaces, 90% incident light is reflected. Can a surface be considered polished for some waves and not for others? Yes. The mesh of a radio dish is polished (good reflector) for long wavelength radio waves and yet rough for short wavelength light waves. (diffuse reflection in many directions) How does the angle at which a ray of light strikes a pane of window glass compare with the angle at which it passes out the other side? The angles are the same. The emerging light is displaced but parallel to the incident light. When is the angle at which a ray of light strikes glass not the same as the angle it exits? When the light strikes the glass in one medium (such as air) and exits the glass in another medium (such as water) In which medium does light travel faster - thin air or dense air? How does this affect the length of daylight hours? It travels faster in thin air, which makes sunlight curve and extends the length of the day. Does the law of reflection hold for curved mirrors? Yes. It is as if the curved mirror is made of many small plane mirrors at slightly different orientations to each other. "At each point, the angle of incidence is equal to the angle of reflection. The normals at different points on a surface are not parallel to one another." In convex or concave mirror, the law of reflection applies. Is a mirage the result of reflection or refraction? Why does it happen? Refraction. Light curves through warm, low-density air near the ground, where it travels faster. "The apparent 'wetness' of the road is not a reflection of the sky by water but rather refraction of sky light through hotter, less dense air near the road surface." *Refraction is simply a consequence of light having different avg speeds in different media." When the wheel of a cart rolls from a smooth sidewalk onto a plot of grass, the interaction of the wheel with the blades of grass slows the wheel. What slows light when it passes from air into glass or water? The light oscillates electrons in the atoms of the glass or water. The electrons absorb some of the energy and reemit it after a delay at each atom. What is the angle between a light ray and its wavefront? a right angle. "The light ray remains perpendicular to the wavefront and therefore bends at the surface." Wavefront: crest, trough, any continuous portion of a wave. What is the relationship between index of refraction and the speed of light in a material? The index of refraction is inversely proportional to the speed of light in a material. Index of Refraction (n) = speed of light in vacuum / speed of light in material. Snell's Law (Quantitative Law of Refraction): n1 sin θ1 = n2 sin θ2. for a vacuum, n = 1. Are eyeglasses made with "high index of refraction" materials thinner or thicker? Why? Thinner. Light bends more entering high index of refraction materials. "The greater the n, the greater the bending of light in the lens, which translates into less lens thickness." The n of high-index plastic lenses reaches 1.76, so light slows more and bends more, and lenses can be made thinner- good news for nearsighted people who want thinner eyeglasses. How does refraction change the apparent depth of a swimming pool? It makes the pool look shallower - only ¾ as deep. "Looking straight down into water, an object submerged 4m beneath the surface appears only 3 m deep. Because of refraction, it appears to be closer, bigger." Which travels more slowly in glass, red light or violet light? Why? Violet light travels slower because it is closer in frequency to the ultraviolet resonance of the atoms in the glass. Since the natural or resonant frequency of most transparent materials is in the ultraviolet part of the spectrum, higherfrequency light travels more slowly that lower-frequency light." Violet light travels about 1% slower in ordinary glass than red light. Light waves with colors between red and violet travel at their own intermediate speeds. Does a single raindrop illuminated by sunlight deflect light of a single color or does it disperse a spectrum of colors? Does it do this by reflection, refraction, or both? It disperses a spectrum of colors, by both reflection and refraction. "Each color is partly refracted out into the air, and partly reflected back into the water." Does a viewer see a single color or a spectrum of colors coming from a single faraway drop? A viewer sees a single color from a single faraway drop. "Although each drop disperses a full spectrum of colors, an observer is in a position to see the concentrated light of only a single color from any one drop." Why is a secondary rainbow dimmer than a primary bow? How are the colors arranged in the secondary bow? There is a second reflection with a loss of light. The colors are in the opposite order of the primary bow, with red on the inside instead of the outside. "Double reflection in a drop produces a secondary bow. Because of this extra reflection (and extra refraction loss), the secondary bow is much dimmer and its colors are reversed." What is meant by critical angle? The minimum angle of incidence inside a medium where light is totally reflected. A beam of light no longer emerges into the air above the surface. Just below this angle, the intensity of the emerging beam reduces to zero and grazes the surface (fig. 28.37) At what angle inside glass is light totally internally reflected? At what angle inside a diamond is light totally internally reflected? 43° for glass. Light in the glass, incident at angles larger than 43° to the surface, is totally internally reflected. 24.5° for diamond. Most light incident on the sloped backsides at angles larger than 24.5° is totally internally reflected. Light normally travels in straight lines, but it "bends" in an optical fiber. Explain. Total internal reflection keeps the light trapped inside the optical fiber. Distinguish between a converging lens and a diverging lens. When two parallel rays of light pass through a converging lens, the rays bend towards each other. When they pass through a diverging lens, the rays move apart from each other. What is the focal length of a lens? What is the focal point? The distance between the center of the lens and either focal point is the focal length. The focal point is the point where a beam of parallel light, parallel to the principal axis, converges or appears to converge. Distinguish between a virtual image and a real image. Mention in each case whether the image made by a single lens is right-side up or inverted. A virtual image, unlike a real image, cannot be displayed on a screen. A virtual image is upright, whereas a real image is inverted. What kind of lens can be used to produce a real image? A virtual image? A real image can only be made with a converging lens (light rays converge at the location of the image, can be displayed on a screen). A virtual image can be made with either a converging or diverging lens. What is astigmatism, and how can it be corrected? Astigmatism is caused when the cornea has a different radius of curvature in one direction compared to another. It is cured by adding a lens with a different radius of curvature in two different directions. "The cylindrical lenses have more curvature in one direction than in another." Why is vision sharpest when the pupils of the eye are very small? Light passes only through the center of the lens, where aberrations are minimal What is wrong with the cartoon of the man looking at himself in the mirror? (Have a friend face a mirror as shown, and you'll see.) his reflection is too close to the mirror surface! The reflection would show a different portion of the face than what is depicted, more like the actual photo above it on the page. If, while standing on a bank, you wish to spear a small blue fish beneath the water surface in front of you, should you aim above, below, or directly at the observed fish to make a direct hit? If, instead, you zap the fish with a red laser, should you aim above, below, or directly at the observed fish? Defend your answers. Spear: Below because of refraction the speed of light is slower in water. Laser: Directly at it, the water will bend the light aiming it at the fish because of refraction. Fermat's principle is of least time rather than of least distance. Would least distance apply as well for reflection? For refraction? Why are your answers different? For reflection, yes, since the light stays in the same medium and has a constant speed. For refraction, no. The light enters a different medium which a different speed. the path of least time is no longer the same as the shortest path. Why is the lettering on the front of some vehicles "backward" This is so that drivers in front of the ambulance, when viewing their rear-view mirrors, will see the correct phrase as reflected! Car mirrors are uncoated on the front surface and silvered on the back surface. When the mirror is properly adjusted, light from behind reflects from the silvered surface into the driver's eyes. Good. But this is not so good at nighttime with the glare of headlights behind. This problem is solved by the wedge shape of the mirror (see sketch). When the mirror is tilted slightly upward to the "nighttime" position, glare is directed upward toward the ceiling, away from the driver's eyes. Yet the driver can still see cars behind in the mirror. Explain The mirror is wedge shaped; in normal position, the silvered back surface is responsible for the reflection into the driver's eyes. By tilted the wedge angle of the glass up, the silvered surface (reflective) goes up too; a dramatic reduction of brightness (glare) from the car behind. However, the driver can still see cars behind. Hold a pocket mirror almost at arm's length from your face and note how much of your face you can see. To see more of your face, should you hold the mirror closer or farther away, or would you have to have a larger mirror? (Try it and see!) A larger mirror is actually needed to see more of your face! Simply bringing the pocket mirror further from your face does not "zoom out" and fit more image in the reflective surface. The image still fills out the parameters of the surface. Relative to the distance of an object in front of a plane of mirror, how far behind the mirror is the image Image is the same distance behind the plane mirror as the object in front of it What fraction of the light shining straight at a piece of clear glass is reflected from the first surface 4% Can a surface be considered polished for some waves and not for others Yes. The mesh of a radio dish is polished for long wavelength radio waves and yet rough for short wavelength first waves Does light travel faster in think or thick air. How does it affect daylight hours Travels faster in thin air, which makes sunlight curve and extends length of the day Is a mirage the result of reflection or refraction Refraction. Light curved thru warm , low density air near the ground where it travels faster What is the relationship between index of refraction and the speed of light In a material Index of a refraction is inversely proportional to speed of light in a material Are eyeglasses made with "high index of refraction" thinner or thicker Thinner. Iight bends more entering high index of refraction materials Which travels more slowly in glass, red or violet light Violet bc it's closer in freq to ultraviolet resonance of the atoms in the glass Does a single rains drop illuminated by sunlight deflect light of a single color or does ir disperse a spectrum of colors It disperse a spectrum of colors by both reflections and refraction Does a viewer see a single color of a spectrum of colors coming from a single faraway drop Single color from a single faraway drop Light normally travels in straight lines, but it bends in optical fiber Total internal reflection keeps the light trapped inside the optical fiber Virtual vs real image Cannot be displayed on a screen. Virtual is upright, real is inverted What kind of lens can be used to produce a real and virtual image Real- converging lens Virtual- either converging or diverging When a flashlight submerged in water shines up into air above, does speed of light increase or decrease when light passes from water to air Increase Waves spread when passing thru openings of various sizes, more spreading occurs for openings that are Narrow Is interference restricted to only some types of waves or does it occur for all types of waves All What phenomenon distinguishes longitudinal waves from transverse waves Polarization Hologram is result of light Interference If the atmosphere were about 40 times thicker, at noon the sun would appear red-orange The color of an opaque object is the same as the light that is reflected. The whiteness of clouds is evidence in the clouds for a variety of particle sizes. Colors seen on the cover of our physics book result from color subtraction Which will warm up quicker in sunlight? a piece of colored glass While Earth is experiencing a total solar eclipse, an observer on the side of the moon facing the Earth would see a tiny dark spot move across the face of Earth. Things seen by moonlight usually aren't colored because moonlight is too dim to activate the retina's cones. Infrared waves are often called heat waves because they induce resonance in molecules and increase internal energy in a substance. Which of these electromagnetic waves has the shortest wavelength? X-rays If the sun were to disappear right now, we wouldn't know about it for 8 minutes because it takes 8 minutes for light to travel from the sun to the Earth. Complementary colors are two colors that produce white light when added together. The solar radiation curve is a plot of brightness of sunlight versus its frequency. A whitish sky is evidence that the atmosphere contains a mixture of particle sizes. The greenish blue of water is evidence for the absorption of red light. A mixture of red and green pigments appears blackish brown. Electromagnetic waves consist of oscillating electric and magnetic fields. A pair of sunglasses and a pair of clear reading glasses are left in the sunlight. The hotter glasses would be the sunglasses At the same time an astronaut on the moon sees a solar eclipse, observers on Earth see a lunar eclipse. What is the frequency of an electromagnetic wave that has a wavelength of 300,000 km? 1 Hz its frequency Color depends on what characteristic of light? its amplitude its frequency both of these absorbed. When the frequency of light matches the natural frequency of molecules in a material, light is transmitted. absorbed. reflected. none of these reflected. The color of an opaque object is the same as the light that is transmitted. reflected. absorbed. all of these none of these blue What color light is transmitted by a piece of blue glass? red white orange blue yellow yellow-green. The brightest color emitted by the sun is violet. yellow-green. red. green-blue. orange. c) a plot of brightness of sunlight versus its frequency. The solar radiation curve is a) a dent in the otherwise spherical sun b) the path taken by the sun as it travels around the Earth c) a plot of brightness of sunlight versus its frequency d) a plot of the colors of sunlight versus their frequencies e) a plot of light intensity versus distance from the sun B) green glass. Light shines on a pane of green glass and a pane of clear glass. The temperature will be higher in the A) clear glass. B) green glass. C) Neither - it will be the same in each. B) red, blue, green. The colored dots that make up the color on a TV screen are A) magenta, cyan, yellow. B) red, blue, green. C) yellow, blue, green. D) red, green, yellow. E) red, blue, yellow. a) additive If three primary colors of light are to shine on a white wall to produce a white spot, the primaries must be a) additive b) subtractive c) multiplicative d) divisive C) yellow. The complementary color of blue is A) red. B) green. C) yellow. D) cyan. E) magenta. D) produce white light when added together. Complementary colors are two colors that A) look good together. B) are additive primary colors. C) are subtractive primary colors. D) produce white light when added together. E) are right for each other. addition. Colors seen on TV results from color addition. subtraction. either of these neither of these B) subtraction. Colors seen on the cover of our physics book result from color A) addition. B) subtraction. C) either of these D) neither of these A) red and blue light. Magenta light is really a mixture of A) red and blue light. B) red and cyan light. C) red and yellow light. D) yellow and green light. E) none of these d) frequencies Different colors of light correspond to different light a) velocities b) intensities c) polarities d) frequencies e) none of these b) green A mixture of cyan and yellow pigments appears a) orange b) green c) magenta d) blue e) blackish brown D) magenta, cyan, yellow, and black. Look at a full-color picture in a magazine with a magnifying glass and you'll see that the inks used are A) red, green, and blue. B) red, green, blue, and black. C) magenta, cyan, and yellow. D) magenta, cyan, yellow, and black. E) none of these resonators which scatter blue light. The sky is blue because air molecules in the sky act as tiny A) mirrors which reflect only blue light. B) resonators which scatter blue light. C) sources of white light. D) prisms. E) none of these B) small particles Which interacts more with light of relatively high frequencies? A) large particles B) small particles C) both the same C) a mixture of particle sizes. A whitish sky is evidence that the atmosphere contains A) predominantly small particles. B) predominantly large particles. C) a mixture of particle sizes. D) water vapor. E) pollutants. D) survive being scattered in the air. Red sunsets are due to lower frequencies of light that A) are scattered from larger particles in the air. B) are refracted from larger particles in the air. C) are reflected by clouds and relatively large particles in the air. D) survive being scattered in the air. E) appear reddish orange to the eye. C) just after a rainstorm. The sky is the deepest blue A) just before a rainstorm. B) during a rainstorm. C) just after a rainstorm. D) when the air is humid. E) just before sunset. A) water droplet sizes. The whiteness of clouds is evidence in the clouds for a variety of A) water droplet sizes. B) molecules. C) "seeds" upon which condensation of cloud material forms. D) light intensities. E) water prisms. E) no color - black. A red crab very deep in water, where sunlight is dim, appears A) red. B) orange. C) cyan. D) brown. E) no color - black. cyan light. A sheet of red paper will look black when illuminated with A) red light. B) yellow light. C) magenta light. D) cyan light. E) none of these A) magenta. If sunlight were green instead of white, the most comfortable color to wear on a cold day would be A) magenta. B) yellow. C) green. D) blue. E) violet. A) refraction of sunsets and sunrises all around the world. The redness of the lunar eclipse is evidence for the A) refraction of sunsets and sunrises all around the world. B) infrared light continually emitted by the moon. C) scattering of lower frequencies of light by the moon. D) faintly radiating atoms in our own atmosphere when sunlight is not incident upon them. E) dim light that is incident upon the moon by Jupiter and other planets. A) red-orange. If the atmosphere were about 40 times thicker, at noon the sun would appear A) red-orange. B) orange-green. C) green-blue. D) blue-violet. E) none of these A) atmosphere between the observer and the hills. Distant dark colored hills appear blue because that is the color of the A) atmosphere between the observer and the hills. B) selectively reflected light that reaches a distant observer. C) reflected light that survives scattering. D) sky that is reflected off the hills. Paint Pigments are tiny particles that absorb specific colors Complementary Colors Red + Blue = Magenta Red + Green = Yellow Blue + Green = Cyan subtractive color mixing How does colored paint mix? Absorption Most things we see do not produce light themselves. Instead they reflect or transmit part of the light that shines on them. The rest of the light is absorbed. complementary color for any given color on the color wheel, the color exactly opposite it is called it's complementary color secondary light colors what you get when you combine two primary colors. yellow, magenta, and cyan White paint White paint No pigment produces Black paint mix all three colors: cyan, yellow, and magenta or CYM. and you get White light White light all three primary colors gives you black the absence of light subtractive color mixing involves pigments like those in paint or ink. The primary colors for Paint are cyan, yellow, and magenta or CYM. additive color mixing nvolves mixing different colors of Light. Specifically, red, green, and blue or RGB. How does colored light mix additive color mixing Isaac Newton first became famous for his contributions to the understanding of: A) the laws of mechanics. B) the law of gravity. C) light. C) light. Strictly speaking, to say that an apple is red means that A) is, or appears makes no differencered is red. B) an apple is red. C) it appears red. C) it appears red. What characteristic of light mostly relates to color? A) frequency B) amplitude C) both of these A) frequency Different colors of light correspond to different light A) intensities. B) velocities. C) frequencies. D) polarities. E) none of the above C) frequencies. When the frequency of light matches the natural frequency of molecules in a material, light is A) absorbed. B) transmitted. C) reflected. D) none of the above A) absorbed. The color of an opaque object is the same as the light that is A) transmitted. B) reflected. C) absorbed. D) all of the above E) none of the above B) reflected. You can get a sunburn while under the "shade" of a beach umbrella due to A) reflected sunlight from the sand. B) light scattering in the air. C) refracted sunlight from the water. D) none of the above A) reflected sunlight from the sand. A blueberry will look black when illuminated with A) cyan light. B) magenta light. C) yellow light. D) none of the above C) yellow light. A red apple will appear black when illuminated with A) magenta light. B) cyan light. C) blue light. D) yellow light. E) none of the above B) cyan light. A banana will appear black when illuminated with A) black light. B) blue light. C) green light. D) red light. B) blue light. If sunlight were green instead of white, the most comfortable color to wear on a hot day would be A) magenta. B) violet. C) blue. D) green. E) yellow. D) green. If sunlight were green instead of white, the most comfortable color to wear on a cold day would be A) green. B) violet. C) blue. D) yellow. E) magenta. E) magenta. What color light is transmitted by a piece of blue glass? A) yellow B) red C) blue D) orange E) white C) blue What color is fully transmitted in common window glass? A) yellow B) green C) blue D) red E) all of the above E) all of the above Which piece of glass will warm up quicker in sunlight? A) colored glass B) clear glass C) both the same A) colored glass Light shines on a pane of green glass and a pane of clear glass. The temperature will be higher in the A) green glass. B) clear glass. C) both the same A) green glass. A fast-moving ball is more easily seen if it is A) red. B) violet. C) green-blue. D) yellow-green. E) orange. D) yellow-green. The solar radiation curve is A) a dent in the spherical Sun. B) a plot of light intensity versus temperature of the Sun. C) the path of the Sun as it circles Earth. D) a plot of Sun's brightness versus frequency of emission. E) a plot of sunlight colors versus their frequencies. D) a plot of Sun's brightness versus frequency of emission. The LEDs that make up the color on some TV screens are A) yellow, blue, green. B) magenta, cyan, yellow. C) red, blue, green. D) red, blue, yellow. E) red, green, yellow. C) red, blue, green. Colors seen on some TV screens result from color A) subtraction. B) addition. C) either of these D) neither of these B) addition. If three primary colors of light shine on a white wall and produce a white spot, the primaries must be A) subtractive. B) multiplicative. C) additive. D) divisive. C) additive. Which is not a color? A) yellow-green B) black C) both of these D) neither of these B) black The brightest color in sunlight is A) violet. B) green. C) yellow. D) red. E) yellow-green. E) yellow-green. The Sun is not seen as yellow-green because A) its brightness is only slightly greater than the other colors. B) it is small part of a mixture of other colors in sunlight. C) it is not yellow-green. D) our vision is not adapted to yellow-green. B) it is small part of a mixture of other colors in sunlight. Stare at a red wall for a few minutes and then gaze at a white wall. Due to retina fatigue you see A) more red. B) black. C) cyan. C) cyan. Complementary colors are two colors that A) produce white light when added. B) are additive primary colors. C) are right for each other. D) produce white light when subtracted. E) blend together. A) produce white light when added. The complementary color of blue is A) yellow. B) cyan. C) red. D) green. E) magenta. A) yellow. If only one color is absorbed in the pigment of a particular blue paint, that color would be A) red. B) yellow. C) blue. D) green. B) yellow. How many colors of ink are used to print full-color pictures? A) two plus black B) one plus black C) three plus black D) six plus black E) four plus black C) three plus black Look at full-color photos in your textbook with a magnifying glass and you'll see inks of A) red, green, blue, and black. B) magenta, cyan, and yellow. C) red, green, and blue. D) magenta, cyan, yellow, and black. E) none of these D) magenta, cyan, yellow, and black. A mixture of red and green pigments appears A) orange. B) blue. C) muddy-brown. D) yellow. E) magenta. C) muddy-brown. Magenta light is a mixture of A) red and yellow light. B) yellow and green light. C) red and blue light. D) red and cyan light. E) none of the above C) red and blue light. A mixture of cyan and yellow pigments appears A) blackish-brown. B) green. C) magenta. D) orange. E) blue. B) green. Which interacts more with high-frequency sounds? A) large bells B) small bells C) both the same B) small bells Which interacts more with high-frequency light? A) small particles B) large particles C) both the same A) small particles Distant bright snowy mountains appear yellowish because A) of nature's wonderful preferences. B) blue has been scattered away from light reflected from the mountains. C) they are far away. D) the color yellow looks just right. B) blue has been scattered away from light reflected from the mountains. Distant dark mountains appear bluish because A) they are far away. B) of nature's wonderful preferences. C) yellow is being scattered. D) you're looking at low-level blue sky between you and the mountain. D) you're looking at low-level blue sky between you and the mountain. The sky is blue because air molecules in the sky act as tiny A) sources of white light. B) prisms. C) mirrors which reflect only blue light. D) optical tuning forks that scatter blue light. E) none of the above D) optical tuning forks that scatter blue light. The sky is usually the deepest blue A) just before sunset. B) during a rainstorm. C) when the air is humid. D) just before a rainstorm. E) just after a rainstorm. E) just after a rainstorm. If Earth's atmosphere were appreciably thicker, snow would appear A) still white. B) yellow. C) ultraviolet. D) blue. B) yellow. If the atmosphere were about 40 times thicker, the Sun at noon would appear A) red-orange. B) blue-violet. C) green-blue. D) orange-green. A) red-orange. The atmosphere of Jupiter is more than 1000 km thick. From Jupiter's surface, the Sun at noon would appear A) not at all. B) faintly white. C) white. D) none of the above D) none of the above Light travels slightly slower in the A) upper atmosphere. B) lower atmosphere. C) neither of these B) lower atmosphere. A setting Sun appears red due to A) absorption by smaller particles in the air. B) light's longer path through air at sunset. C) lower frequencies of light emitted during sunset. D) scattering of lower frequencies by larger particles in the air. B) light's longer path through air at sunset. Red sunsets are due to light of lower frequencies that A) survive being scattered in the air. B) are reflected by clouds and relatively large particles in the air. C) are scattered from smaller particles in the air. D) appear reddish-orange to the eye. E) are scattered from larger particles in the air. A) survive being scattered in the air. If molecules in the sky scattered orange light instead of blue light, sunsets would be colored A) orange. B) green. C) yellow. D) blue. E) none of the above D) blue. On a planet in the solar system where the sky normally scatters light of lower frequencies, its sunsets would be A) bluish. B) whitish. C) yellow-greenish. D) reddish. A) bluish. On a planet where atmospheric gases are red, distant dark mountains would appear A) greenish. B) yellowish. C) bluish. D) reddish. E) untinted. D) reddish. On a planet where atmospheric gases are yellow, distant snow covered hills would look A) greenish. B) bluish. C) yellowish. D) reddish. E) untinted. B) bluish. The redness of the lunar eclipse is due to A) dim light that is incident upon the Moon by Jupiter and other planets. B) infrared light continually emitted by the Moon. C) refraction of sunsets and sunrises all around Earth. D) scattering of lower frequencies of light by the Moon. C) refraction of sunsets and sunrises all around Earth. The whiteness of clouds, unlike the blueness of the sky, primarily involves A) water prisms. B) medium sized particles. C) reflection and refraction of sunlight. D) seeds upon which condensation of cloud material forms. C) reflection and refraction of sunlight. Compared to smaller clouds with small droplets, a big cloud with large droplets A) is more likely to produce rain. B) is darker. C) absorbs more light. D) all the above E) none of the above D) all the above The darkness of clouds is due to A) absorption. B) often being in the shadow of another cloud. C) both of these D) neither of these C) both of these The greenish blue of water is evidence for the A) reflection of red light. B) interaction between green and blue frequencies of light. C) absorption of red light. D) absorption of greenish-blue light. E) reflection of greenish-blue light. C) absorption of red light. The part of the electromagnetic spectrum most absorbed by water is A) red. B) cyan. C) infrared. D) all about equally. C) infrared. The part of the visible spectrum most absorbed by water is A) infrared. B) red. C) cyan. D) all about equally. B) red. The extraordinary blueness in lakes in the Canadian Rockies is the result of A) high-altitude refraction of light. B) the unique temperatures of these lakes throughout most of the year. C) glacial silt in the water scattering blue light. D) none of the above C) glacial silt in the water scattering blue light. A white boat sunk in water where sunlight is dim appears A) no colorblack. B) red. C) cyan. D) yellow. C) cyan. A red crab very deep in water, where sunlight is dim, appears A) no color|black. B) cyan. C) orange. D) brown. E) red. A) no colorblack. (A) Yellow light + blue light = _______ light (B) Green light + _______ light = white light (C) Magenta + yellow + cyan = _______ light (A) white (B) magenta (C) white TRUE or FALSE (A) Red + green + blue = white (B) Red + green = yellow = white - blue (C) Red + blue = magenta = white - green (D) Fill in the last statement. Green + blue = cyan = white - _______ (A) true (B) true (C) true (D) red Your friend says that the reason the distant dark mountains appear blue is because you're looking at the sky between you and the mountains. Do you agree or disagree? I agree 1) Light is reflected when A) electron clouds of atoms are energized. B) atomic nuclei are made to vibrate. C) incident light is returned into the medium from which it came. D) electromagnetic waves emanate from matter. c 2) When sunlight illuminates a page from your Conceptual Physics book it A) reflects most of it. B) absorbs at the text lettering. C) both of these D) neither of these c 3) Light travels from one place to another along a path of least A) distance. B) time. C) effort. D) expense. E) complication. b 6) According to the law of reflection, the incident light ray, the reflected light ray, and the normal between them A) lie in the same plane. B) may or may not lie in the same plane. C) lie in planes that are perpendicular to one another. a 7) Object and image for a plane mirror occur A) along the same plane. B) equal distances from the mirror. C) at right angles to each other. D) all of the above E) none of the above b 8) The inversion of your image in a plane mirror is actually an inversion of A) left-right. B) up-down. C) front-back. D) all of the above c 10) Diffuse reflection occurs when the size of surface irregularities is A) small compared to the wavelength of the light used. B) large compared to the wavelength of the light used. C) microscopic. b 11) Your image in a plane mirror is A) virtual. B) real. C) both of these D) neither of these a 12) A rough surface for infrared waves may be polished for A) radio waves. B) light waves. C) both of these D) neither of these a 13) When light reflects from a surface, there is a change in its A) frequency. B) wavelength. C) speed. D) all of the above E) none of the above e 14) A yellow candle flame reflects from opposite surfaces of a piece of red glass. A) both images are yellow B) one image is yellow and the other red C) both images are red D) both images are reddish yellow b 15) You photograph the image of your little sister, who stands 2 meters in front of a plane mirror. Holding the camera beside her head, the distance to her image is A) 1 meter. B) 2 meters. C) 3 meters. D) 4 meters. E) none of the above d 16) If you walk towards a mirror at a certain speed, the relative speed between you and your image is A) half your speed. B) your speed. C) twice your speed. D) none of the above c 17) The shortest plane mirror in which you can see your entire image is A) half your height. B) about 3/4 your height. C) about 1/3 your height. D) equal to your height. E) dependent on your distance from the mirror a 18) To see his full height, Blinky Bill who is 1 meter tall needs a mirror that is at least A) 0.33 m tall. B) 0.50 m tall. C) 0.75 m tall. D) 1 m tall. E) depends on distance from the mirror. b 19) If you look at yourself in a pocket mirror, then hold the mirror farther away, you see A) more of yourself. B) less of yourself. C) the same amount of yourself. c 20) In looking at yourself in a steamy mirror you wipe just enough moisture away to barely see a full view of your face. If you move back from the mirror you'll see A) a bit more of your face. B) a bit less of your face. C) the same amount of your face. c 21) It is difficult to see the roadway when driving on a rainy night mainly because A) light scatters from raindrops and reduces the amount of light reaching your eyes. B) of additional condensation on the inner surface of the windshield. C) the film of water on your windshield provides an additional reflecting surface. D) the film of water on the roadway makes the road less diffuse. E) none of the above d 22) Reflected light from the Moon in a lake often appears as a vertical column when the water is A) perfectly still. B) slightly rough. C) very rough as with churning waves b 23) Standing at the shore of a still lake, the reflected view of scenery on the other side of the lake is the view you would see if you were upside down with your eye in the line of sight A) where it already is. B) at the surface of the water where the light reflects. C) directly beneath you, as far below water level as you are above. D) close to the distant shore. E) none of the above c 24) When a mirror with a fixed beam on it is rotated through a certain angle, the reflected beam is rotated through an angle that is A) equal to the angle of rotation. B) twice as large. C) four times as large. D) none of these b 25) Ninety-five percent of light incident on a mirror is reflected. How much light is reflected when three of these mirrors are arranged so light reflects from one after the other? A) 81% B) 85% C) 86% D) 90% E) 95% c 26) Ninety percent of light incident on a certain piece of glass passes through it. How much light passes through two pieces of this glass? A) 80% B) 81% C) 85% D) 89% E) 90% b 27) Refraction occurs when light passing from one medium to another A) changes frequency. B) changes speed. C) loses energy. D) reflects inward. b 28) Refraction results from differences in light's A) frequency. B) incident angles. C) speed. D) all of the above E) none of the above c 29) Light refracts when traveling from air into glass because of a change in light's A) intensity. B) frequency. C) speed. D) all of the above E) none of the above c 30) Light travels fastest in A) warm air. B) cool air. C) a vacuum. c 31) When a light ray in air enters water at 15° from the normal, it A) always bends toward the normal. B) always bends away from the normal. C) sometimes bends towards or away from the normal. D) does not bend. a 32) When a light ray passes at a non-90° angle from water into air, it A) bends toward the normal. B) bends away from the normal. C) travels much slower. b 33) When light passes through common windowpane, its angle of emergence is A) usually less than its angle of incidence. B) always less than its angle of incidence. C) the same as its angle of incidence. D) usually more than its angle of incidence. E) always more than its angle of incidence. c 34) A mirage is a result of atmospheric A) reflection. B) refraction. C) scattering. D) dispersion. E) aberrations. b 35) The twinkling of the stars is a result of atmospheric A) reflection. B) refraction. C) scattering. D) dispersion. E) aberrations. b 36) Refraction causes the bottom of a swimming pool to appear A) farther down than it actually is. B) closer to the surface than it actually is. C) neither of these b 37) The average speed of light is greatest in A) red glass. B) orange glass. C) green glass. D) blue glass. E) same in all of these a 38) In which material does light travel fastest? A) glass B) water C) plastic D) air E) same for all d 39) Atmospheric refraction makes the daylight hours a bit A) longer. B) shorter. C) longer in summer but shorter in winter. a 40) When a pulse of white light is incident on a glass prism, the first color to emerge is A) red. B) orange. C) green. D) violet. a 41) A fish above the surface of water will see better in air if it has goggles that are A) tinted blue. B) hemispherical. C) filled with water. D) extremely shiny. E) none of the above c 42) Stars twinkle when seen from Earth. When seen by an astronaut on the Moon, stars A) twinkle more. B) twinkle less. C) don't twinkle. c 44) If the speed of light in a sphere is 2 × 108 m/s, its index of refraction is A) 0.50. B) 0.67. C) 1.0. D) 1.5. E) 2.0. d 45) Stephanie dips a glass rod into vegetable oil. The submerged part of the rod can't be seen because A) refraction is unbent before light gets to your eye. B) both the oil and glass have the same index of refraction. C) of internal reflection. D) light has different speeds in the oil and glass. b 46) When spearing a fish with a regular spear, to compensate for refraction, throw your spear A) directly at the sighted fish. B) above the sighted fish. C) below the sighted fish. c 47) To "spear" a red fish with a red laser beam and compensate for refraction, aim your laser A) directly at the sighted fish. B) above the sighted fish. C) below the sighted fish. a 49) To send a beam laser-light beam to a space station just above the atmosphere near the horizon, aim your laser A) above your line of sight. B) below your line of sight. C) along your line of sight. c 50) The index of refraction for crown glass, common in eyeglasses, is 1.52. The index of refraction of a particular plastic lens is 1.76. Light bends more in the A) crown glass. B) plastic lens. C) same speed in each. D) need more information b 56) A person standing waist-deep in a swimming pool appears to have short legs because of light A) reflection. B) absorption. C) interference. D) diffraction. E) refraction. e 57) Light of different colors in a vacuum travel at A) different speeds. B) the same speed. C) the same speed in both a vacuum and all materials. b 58) Light of different colors in a glass prism travel at A) different speeds. B) the same speed. C) the same speed in prisms and all materials. a 59) Which are consequences of different speeds of light in different media? A) mirages B) rainbows C) brilliant colors of diamonds D) all of the above E) none of the above d 61) As monochromatic light passes from air to glass and back to air, changes occur in its A) wavelength. B) speed. C) both of these D) neither of these c 62) A mirage occurs when light travels faster A) near the ground than higher up. B) in less dense air than more dense air higher up. C) both of these D) neither of these c 63) A mirage occurs for road surfaces that are most often A) hot. B) cold. C) wet. D) hard. E) snowy. a 64) When sunlight from air enters water, light that refracts most is A) red. B) orange. C) green. D) violet. E) all refract the same amount d 65) Rainbows exist because light is A) reflected. B) refracted. C) both of these D) neither of these c 66) A single raindrop illuminated by sunshine disperses A) a single color. B) mainly light of mid-frequency colors. C) all the colors of the rainbow. c 67) Rainbows are not usually seen as complete circles because A) the ground is usually in the way. B) they are actually elliptical. C) they have no bottom part. D) rain drops are not perfectly round. E) rainbows are actually arched shaped. a 68) When a rainbow is seen as a complete circle from an airplane, the airplane's shadow is A) in the center of the rainbow. B) in the lower part of the rainbow. C) in the upper part of the rainbow. D) totally outside the rainbow. E) nowhere, for there is no shadow. a 71) If you view a rainbow out your window while riding in a train, you'll see that A) the rainbow can only be seen while you're moving slowly or at rest. B) the rainbow moves along with you. C) you soon pass by it, leaving it where you first saw it. b 72) The critical angle for a transparent material is the angle at and beyond which all light within the material at its upper surface is A) refracted. B) reflected. C) absorbed. D) dispersed. E) diffused. b 75) When a light beam emerges from water into air, light speed A) increases. B) decreases. C) remains the same. a 76) The critical angle is least in A) glass. B) water. C) diamond. D) vacuum. c 77) A diver shines light upward to the surface of a smooth pond at 20° to the normal. Most light passes into the air above while the part that reflects back into the water makes an angle to the normal of A) less than 20°. B) 20°. C) more than 20°. D) all refracts, none reflects. Answer: B b 79) At night an underwater scuba diver aims a flashlight beam toward the surface at 15° to the normal. Upon emerging into the air, the beam angle will be A) less than 15°. B) 15°. C) more than 15°. D) impossible to predict. c 80) The refraction of light in a diamond is greater for A) long-wavelength light. B) short-wavelength light. C) both refract the same b 81) In optical fibers of uniform density, light actually A) curves in a direction parallel to the central axis of the fiber. B) travels in straight-line segments. C) travels along the outer surface of the fiber. D) none of the above b 82) Optical fibers are commonly used by A) surgeons. B) mechanics. C) engineers. D) aviators. E) all of the above e 83) The type of lens that spreads parallel light is a A) converging lens. B) diverging lens. C) combination of converging-diverging lens. b 84) The type of lens that brings parallel light rays together is a A) converging lens. B) diverging lens. C) combination of converging-diverging lens. a 85) Which of the following can be projected onto a viewing screen? A) a real image B) a virtual image C) both of these D) neither of these a 86) A "burning glass" used to concentrate sunlight in a tiny spot is a A) converging lens. B) diverging lens. C) either of these D) neither of these a 87) Your vision is sharpest when your pupil is A) dilated. B) constricted. C) same either way b 88) The image in a pinhole camera is A) always inverted. B) sometimes inverted. C) always right-side up. a 89) When the tiny hole in a pinhole camera is made larger, the image is A) brighter but less clear. B) clearer. C) right-side up. D) none of the above a 92) In a converging lens, objects infinitely far away are focused A) in front of the focal point. B) at the focal point. C) beyond the focal point. b 93) The image of the "infinitely-far-away" Sun produced by a converging lens appears A) between the lens and the focal point. B) at the focal point. C) beyond the focal point. b 97) Light travels slower in a lens having a A) high index of refraction. B) low index of refraction. C) same in each a 98) When taking a photo of a nearby flower, your camera lens should be set A) closer than one focal length from the photosensitive surface. B) farther than one focal length from the photosensitive surface. C) to one focal length from the photosensitive surface. b 99) Chromatic aberration is a consequence of different colors in a lens having different A) aberrations. B) frequencies. C) energies. D) critical angles. E) speeds. e 100) Chromatic aberration is absent in A) converging lenses B) diverging lenses. C) front surface plane mirrors. c 102) If you cover half a camera lens with opaque tape, the images produced will be A) B) C) D) b cut in half. only dimmer. both of these neither of these