Gravitational vs. Electrical Forces Answers

QUIZ 1 1. A main difference between gravitational and electrical forces is that electrical forces repel or attract. a. They both: attract, obey inverse-square law, reaches infinity, gravity is weak 2. When the distance between two forces are halved, the electrical force between them quadruples. *don’t forget to square “d” a. Calculate electrical force: Coulomb's Law: 𝐹𝐸 = 𝑘 𝑞 1𝑞 2 (inverse square law) 2 𝑑 b. ***variable for charge is “q” 3. Conducting materials are composed of atoms with loose outer electrons. (the charge can flow - electrons free to move around) 4. To say that electric charge is conserved is to say that electric charge can neither be created or destroyed. (charge conservation) a. To say the electric charge is quantized is to say that the electric charge; (Charge Quantization) → may occur in an infinite variety of quantities; is a whole number multiple of the charge of ONE electron (egg example) 5. A positively-charged rod is held near an aluminum can that rests on a dry wood table. If you momentarily touch the opposite side of the can with your finger, the can becomes negatively charged. (charging by induction) QUIZ 2 1. The direction of an electric field is the direction of the force exerted on a proton. (a positive test charge) 2. A 2-C charge is placed in a location where the electric field is 10 N/C. How much electric force is exerted on the charge? 20N a. Electric Field Equation: 𝐸 = 𝐹/𝑞𝑡 3. The primary focus of a lightning rod is to discharge the structure to which it is attached. (so it doesn’t go to your house in the first place) a. Backup plan is to attract the lightning to the ground so it doesn’t hurt anyone 4. How much energy is stored by pushing 4 coulombs of charge into an electric field, where its voltage is 2 V greater compared to its starting position? 8J a. Looking for Energy Stored: 𝑉 = 𝑃.𝐸. 𝑞 b. Volt*Coulomb=Joule 5. A charged balloon neatly illustrates that something can have a great amount of voltage and a small potential energy. a. Used concept of polarization QUIZ 3 1. 6 joules of energy are given to 0.5 coulombs of charge passing through a 12V battery. a. 𝑉 = 𝑃.𝐸. 𝑞 ***REMEMBER UNITS 2. If two copper wires of the same length have different thickness, then the thicker wire has less resistance. (because there is more pathways for electrons to move through) a. Hot wire has more resistance than a cold wire 3. The voltage across a 10-ohm Ω (R) resistor carrying 5 A (current “I”) is more than 20 V. a. Use Ohm's Law: REMEMBER OHMS TRIANGLE /V\ /I | R\ 4. Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? Touching a light fixture. (it has a lot more charge) 5. A generator produces alternating current and a battery produces direct current. QUIZ 4 1. In an AC circuit, the electric field changes in magnitude and direction with time. a. Inverse square law → has to do with electric FORCE b. Direct current has to do with one direction 2. A light bulb with a resistance of 240 ohms is plugged into a 120 V socket. The power dissipated in the lightbulb is 60 W. a. Use power equations: P=IV; P=I(IR); P=I^2 R and use Triangle 3. When we say an appliance ʺuses up electricity,” we mean electric energy dissipates into heat. - converts electricity into other forms of electricity 4. When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is less than the resistance of either lamp. a. Or in series = increases 5. In a household electrical circuit, the wall outlets and room light switches are all connected in parallel. (series = 1 pathway → like breakers; parallel = different pathways → like light switches & hair dryers) QUIZ 5 1. The source of all magnetism is moving electric charge. 2. The field surrounding every movingelectron is always both electric and magnetic. a. Around (non moving) electrons are always electric & sometimes magnetic. b. Field Lines determined by where a positive charge moved 3. Several paper clips dangle from the south pole of a magnet. The induced pole in the bottom of the uppermost paper clip is a south pole. (he used erasers) 4. If a steady magnetic field exerts a force on a moving charge, that force is directed at right angles to the direction of motion AND right angles to the direction of field. a. Hand thing with thumb and pointing 5. If we think of the Earth as a magnet, its magnetic north pole is nearest Australia. a. Magnetic north is geographic south & visa versa QUIZ 6 1. Electromagnetic induction occurs in a coil when there is a change in magnetic field intensity in the coil. Voltage → was result in induction; not cause in induction 2. If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil half as fast through twice the number of loops, the same voltage is induced. a. Faraday's Law - the induced voltage in a coil is directly proportional to the product of the number of loop and the rate at which the magnetic field is changing 3. A device that rotates a coil in a magnetic field in order to output electrical energy is called an electric generator. Use fan blades to get energy stuff 4. The secondary of a transformer is the coil connected to the load (what you’re powering). a. Primary coil goes to the input power line 5. A 12 V source delivers 24 W of power to the input of a step-down transformer with a 6:1 primary to secondary loop ratio. How much current does the transformer output provide? 12 A → took pic of this problem a. Power equation has current: P = IV b. Ohm’s law has current: I = V/R c. Transformer Equation has loops: 𝑉𝑝 #𝑝 𝑉 = #;𝑠 # = loops 𝑠 TEST 1 1. If a steady magnetic field exerts a force on a moving charge, that force is directed at right angles to the direction of the field. 2. As more lamps are put into a series circuit, the overall current in the power source decreases. 3. A toaster plugged into a 120 V outlet draws 4 A of current. What is the resistance of the toaster? 30 ohms 4. A 2-C charge is placed in a location where the electric field is 10 N/C. How much electric force is exerted on the charge? 20 N 5. Two charged particles repel each other with a force F. If the charge of one of the particles is halved and the distance between them is also halved, then the force will be 2 F. 6. In an ac circuit, the electric field changes magnitude and direction with time. 7. The field surrounding every moving electron is always both electric and magnetic. 8. A 9 V source delivers 27 W of power to the input of a step-up transformer with a 1:3 primary to secondary loop ratio. How much current does the transformer output provide? 1A 9. A device that rotates a coil in a magnetic field in order to output electrical energy is called an electric generator. 10. To say that electric charge is quantized is to say that the charge on an object is a whole-number multiple of the charge of one electron. 11. A charged balloon neatly illustrates that something can have a great amount of voltage and a small potential energy. 12. Most commercial alternating current in North America 13. To say that an object is electrically polarized is to say 14. A transformer produces none of the above. Transformers don’t produce anything, they transfer energy from one coil to another (can increase or decrease current.) 15. Several paper clips dangle from the south pole of a magnet. The induced pole in the bottom of the uppermost paper clip is a south pole. 16. If you used a hair dryer today and it drew 12 A of current, about how much power was it using? 17. 6 joules of energy are given to 0.5 coulombs of charge passing through a 12V battery. 18. If 16 J of energy are stored by pushing 4 coulombs of charge into an electric field, the chargeʹs voltage with respect to its starting position is 4 V. 19. Electromagnetic induction occurs in a coil when there is a change in magnetic field intensity in the coil. 20. Conducting materials are composed of atoms with loose outer electrons. 21. The electric field inside an uncharged metal ball is zero. If the ball is negatively charged, the electric field inside the ball is then zero. 22. Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? touching the light fixture 23. In a household electrical circuit, the wall outlets and room light switches are all connected in parallel. 24. The source of all magnetism is moving electric charge. 25. Electrons are made to flow in a wire when there is 26. The direction of an electric field is the direction of the force that the field would exert on a proton. 27. A positively charged rod is held near a metal can that rests on a dry wood table. If you touch the opposite side of the can momentarily with your finger the can is then negatively charged. 28. If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil half as fast through twice the number of loops, the same voltage is induced. 29. The magnetic field lines of a current-carrying coil with many loops of wire 30. The source of electrons lighting an incandescent ac light bulb is 31. As a copper wire is cooled, its electric resistance decreases. 32. A main difference between gravitational and electric forces is that electrical forces repel or attract. 33. When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is less than the resistance of either lamp. QUIZ 7 1. Electromagnetic waves consist of oscillating electric and magnetic fields. 2. The speed of light in a vacuum is 300,000 km/s. 3. The main difference between a radio wave and a light wave is its wavelength OR frequency. 4. Which of the following series of electromagnetic waves are listed in order of decreasing frequency? Gamma ray, x-ray, ultraviolet, visible, infrared, microwave, radio (in increasing wavelength) a. Increasing frequency = radio, micro, infrared, visible, UV, x-ray & gamma 5. What is the frequency of an electromagnetic wave that has a wavelength of 300 km? a. Equation → C = Fλ; 1/s = Hz (Remember speed of light = 300,000 km/s b. 1000 Hz (kilo hertz - also radio #’s are measured this way) QUIZ 8 1. When ultraviolet light is incident upon glass, atoms in the glass resonate. a. Resonating = vibrating large & long time (bump into each other) (L&L) b. Off resonance = vibrating small & short (S&S) 2. Consider light energy that is momentarily absorbed in glass and then re-emitted. Compared to the absorbed light, the frequency of the re-emitted light is the same. 3. Glass is opaque to wave frequencies that match its natural frequency. 4. Red-hot and blue-hot stars appear white to the eye because they are too dim to fire the cones (the ones in your eyes). 5. In the periphery of our vision, we are sensitive to movement, but cannot see color. QUIZ 9 1. What characteristic of light mostly relates to color? Frequency a. Amplitude = intensity (like brightness) 2. For the same wattage, which lamp provides the most light for nighttime viewing? Sodium vapor lamp (b/c it has a yellow/green tint → eyes are most sensitive to this) a. Fluorescent lamps = blue b. Incandescent lamps = red c. LED = any color 3. The colored dots that make up the color on a TV screen are red, green, and blue. These are the additiveprimary colors. a. Mixing colors of light means adding colors at a time b. Subtractiveprimaries are cyan, yellow & magenta c. Blue + Red = Magenta → no Green d. Green + Red = Yellow → no Blue e. Blue + Green = Cyan → no Red 4. If you want to hide a lemon in a basket of limes, illuminate the fruit with cyan light. 5. The sky is blue because air molecules in the sky act as tiny resonators that scatter blue light. QUIZ 10 1. The path that light travels from one point to another will be the path that takes the least time. 2. Your image in a plane mirror is virtual. a. No light coming from the location of the image b. Real image = actual light coming from where you see the image c. Lenses: converge = come together, diverge = spread out d. Front & back are the only thing that’s inverted e. Also the same size 3. Refraction occurs when light passing from one medium to another changes speed. a. Reason = minimize time (Ex: lifeguard thing) 4. When a light ray passes, at a non-90 degree angle, from water into air, it bends away from the normal. a. Slow to fast = away from normal b. Fast to slow = towards the normal 5. A mirage occurs because light travels faster through hot air close to a hot surface. QUIZ 11 1. When white light goes from air into water, the color that refracts the least is red. a. Violet refracts the most 2. When you view a distant rainbow, you view from each single water drop that contributes to the bow a single color. a. Raindrop disperses like a prism (sends colors at different levels) b. Ex: on the board in class w/ the ball & stick 3. A primary rainbow is brighter than a secondary rainbow because there is one less reflection & refraction inside of the water drops. 4. If a fish in a pond looks upward at 50° to the normal, it will see the pond’s bottom. 5. The type of lens that brings parallel light together is a converging lense. a. Diverging lense spreads apart TEST 2 1. 2. 3. 4. The greenish blue of water is evidence for the absorption of red light. In the periphery of our vision, we are sensitive to movement, but cannot see color. The main difference between a radio wave and a light wave is its (two of these). A primary rainbow is brighter than a secondary rainbow because there is one less reflection and refraction inside the water drops. 5. The inversion of your image in a plane mirror is actually an inversion of front - back. 6. Electromagnetic waves consist of oscillating electric and magnetic fields. 7. Materials generally become warmer when light is absorbed by them. 8. The colored dots that make up the color on a TV screen are red, green, and blue. These are the additive primary colors. 9. Refraction occurs when light passing from one medium to another changes speed. 10. Good binoculars use prisms to redirect light through the process of 11. The type of lens that brings parallel light together is a converging lens. 12. Which of the following series of electromagnetic waves are listed in order of decreasing frequency? gamma ray, ultraviolet, visible, infrared, radio 13. Red-hot and blue-hot stars appear white to the eye because they are too dim to fire the cones. 14. If you want to hide a single magenta rose in a bouquet of a dozen red roses, illuminate the flowers with yellow light. 15. A diver shines light up to the surface of a smooth pond at a 10 degree angle to the normal. Some light passes into the air above, and the part that reflects back into the water makes an angle to the normal of 16. If an electron vibrates up and down 1000 times each second, it generates an electromagnetic wave having a frequency of 1000 Hz. 17. For the same wattage, which lamp provides the most light for nighttime viewing? 18. The bending of light as it refracts actually 19. If a fish looks upward at 45 degrees with respect to the waterʹs surface, it will see 20. What is the wavelength of an electromagnetic wave that has a frequency of 15,000,000 hertz? 50 km 21. A mirage occurs because light travels faster through hot air close to a hot surface. 22. The sky is blue because air molecules in the sky act as tiny resonators which scatter blue light. 23. Compared to its average speed in air, the average speed of a beam of light in glass is more less. 24. Most of the waves in the electromagnetic spectrum are invisible. 25. A single raindrop illuminated by sunshine disperses 26. Different colors of light correspond to different light frequencies. 27. When a light ray passes, at a non-90 degree angle, from water into glass, it 28. When white light goes from air into water, the color that refracts the least is red. 29. The speed of light in a vacuum is 300,000 km/s. 30. The cross and X pictures shown in class were an example of pre-thinking by the retina compensating for the blind spot. 31. The path that light travels from one point to another will be the path that takes the least time. 32. A mixture of magenta and yellow pigments appears red. 33. Glass is opaque to light that matches its natural frequencies in which portion of the EM spectrum? Infrared and Ultraviolet (A and C) QUIZ 12 1. According to Huygensʹ Principle, wave fronts are the overlapped crests of tiny secondary waves. 2. Consider long wavelength plane waves incident upon a barrier with a relatively small opening. After passing through the opening, the waves fan out. a. Process is called diffraction 3. Radio waves that diffract more around small buildings are AM. a. FM 100 frequency of mhz (megahertz) b. AM stations are in kilohertz (lower frequencies = longer wavelengths) 4. Interference is a property of light waves, sound waves, water waves. a. All waves can interfere (have both constructive & destructive) 5. Monochromatic (one color) light is directed at two closely-spaced slits. The distance from the first slit to a given point on the screen is exactly one half wavelength greater than the distance from the second slit to the same point on the screen. The light from the two slits at that point produces a dark fringe. a. b/c there's destructive interference (waves don’t perfectly align) b. Constructive interference is when the waves align QUIZ 13 1. Optical flats rely on what phenomenon to test the flatness of surfaces? Interference a. Single color, thin film interference b. What shows if its flat or not, is the interference between the two c. Optical flats depend on interference 2. Interference colors in a soap bubble give evidence that the soap film has two reflecting surfaces AND is thin. a. Why not w/ thick films? → it misses the eye - too far displaced i. Thick films don’t work to get bubble colors 3. Yellow is seen at one place on a soap bubble film. At a slightly thicker region of the film, one would likely see the color magenta. a. Seeing yellow → takes away blue. The bubble film has to be 1/4th a wavelength to take away blue b. Soap bubbles are probs the thinnest thing c. When to a thicker point, then it cancels green and you see magenta d. Even thicker, it cancels red & you see cyan e. BUBBLES CANCEL COLORS that why you don’t see RGB 4. Polarization is a property of transverse waves. a. Transverse waves → vibrations are right angles to where the wave is moving i. Always in right angle direction to where its moving b. Polarization - lining up the transverse vibrations in one direction c. Sound waves CANNOT be polarized b/c they are LONGITUDINAL waves 5. An ideal Polaroid will transmit 50% of nonpolarized light incident on it. How much light is transmitted by two ideal Polaroids that are oriented with their axes perpendicular to each other? 0% because it is blocked a. Vertical polaroid can take in vertical light (blocks horizontal) i. 2 vertical polaroids? 50% of light b/c it ^ b. Horizontal polaroid can take in horizontal (blocks horizontal) c. He did the circle demonstration again QUIZ 14 1. To say that energy levels in an atom are discrete is to say the energy levels are well defined and separate from one another. a. Continuous is the opposite meaning of discrete b. Spelling matters (discreet means private, not discrete) 2. An excited atom is an atom that has one or more displaced electrons. a. Electron’s moving to different levels 3. An atom that absorbs a certain amount of energy can then emit a photon of the same or lower energy. a. The same energy, or energy in steps on the way down (think about the layer things that he drew) 4. An object heated to twice the absolute temperature emits radiation with twice the peak frequency. a. Incandessence is light emission after heating 5. The radiation curve for a ʺred hotʺ object peaks in the infrared region. a. Red hot = peaking in infrared b. White hot = peaking in yellow/green region c. Blue hot = peaking in ultraviolet region QUIZ 15 1. The fact that iron absorption lines occur in the solar spectrum directly indicates that there is iron in the solar atmosphere. a. Emission spectrum looks like: discrete lines on a black background b. Incandescent spectrum: continuous spectrum c. Absorption spectrum: seeing dark lines against a continuous color background (opposite of emission spectrum) 2. Fluorescent materials on display in museums are illuminated with ultraviolet light. 3. Some light switches glow in the dark after the lights are turned off. This is because of a time delay between excitation and de-excitation AKA phosphorescence. → electron gets stuck here for a certain amount of time (doesn’t de-excite immediately) a. Phosphorescence is like fluorescence BUT phosphorescence STAYS at different times (like glow in the dark stuff) 4. The absorption of an infrared photon that excites an atom to emit a green photon violates the law of energy conservation. a. Can't give off more energy than you have b. Absorb infrared, you only have infrared (not enough for green b/c its lower energy than enough for green) 5. Light from a laser is monochromatic, in phase, coherent. (all of these) QUIZ 16 1. Two pulses of light, one red and one blue, have the same energy. The pulse with the greater number of photons is the red. (higher frequency = higher energy) a. Light energy is quantized (comes in certain quantities) i. These quantities/quanta of energy is called photons b. You’ll need more red photons than the blue to get the same amount of energy 2. When a clean surface of potassium metal is exposed to blue light, electrons are emitted. If the intensity of the blue light is increased, which of the following will also increase? The number of electrons ejected per second a. Processed is called thermoelectric effect (shining light on metal) b. Intensity means brightness or number of photons c. Keep it in blue light, then you just have more of it. (blue photons have the same energy amount) d. If it changes frequency, it’ll change color 3. In the double-slit experiment with electrons, the electrons interact when they arrive at the screen in a particle-like way with a pattern produced by traveling in a wave-like way. 4. A bullet and a proton have the same speed. Which has the longer wavelength? The proton (Bullet has shorter) a. Same momentum? The wavelength would be the same 5. The Heisenberg uncertainty principle states that (all of the above) Planckʹs constant sets a limit on accuracy of measurements; we canʹt simultaneously measure exactly both the position and momentum of a particle; we canʹt simultaneously measure exactly a particleʹs energy and time having that energy. [NOT ON TEST OR FINAL] QUIZ 17 1. The Bohr model of the atom is akin to a miniature solar system. 2. A hypothetical atom has six distinct energy states. Assuming all transitions are possible, how many spectral lines can this atom produce? 15 a. 15 different types (going down the stairs & counting them) 3. Heavy atoms are not appreciably larger in size than light atoms because the nuclei of heavy atoms have more electric charge. 4. The main reason electrons occupy discrete orbits in an atom is because the circumference of each orbit is an integral multiple of electronic wavelengths. 5. The Schrödinger equation of quantum mechanics deals with two, mathematical entities: 2 ψ, the wave function that describes where a particle possibly is, and |ψ| , the probability density function that describes where a particle probably is. TEST 3 1. The hottest star is the star that glows 2. An ideal Polaroid will transmit 50% of nonpolarized light incident on it. How much light is transmitted by two ideal Polaroids that are oriented with their axes perpendicular to each other? 0% 3. Interference is a property of light waves, sound waves, water waves (all of these) 4. When a certain photosensitive surface is illuminated with yellow light, no electrons are ejected. The light that will be most likely to cause electrons to be ejected is 5. Fluorescent materials on display in museums are illuminated with ultraviolet light. 6. According to Huygensʹ Principle, wave fronts are the overlapped crests of tiny secondary waves. 7. Optical flats rely on what phenomenon to test the flatness of surfaces? interference 8. An atom that absorbs a certain amount of energy can then emit a photon of the same or lower energy. 9. Some light switches glow in the dark aer the lights are turned off. This is because of a time delay between excitation and de-excitation. 10. In the double-slit experiment with electrons, the electrons interact when they arrive at the screen in a particle-like way with a pattern produced by traveling in a wave-like way. 11. Monochromatic light is directed at two closely-spaced slits. The distance from the first slit to a given point on the screen is exactly one wavelength greater than the distance from the second slit to the same point on the screen. The light from the two slits at that point produces 12. A bullet and a proton have the same momentum. Which has the longer wavelength? Both have the same wavelength. 13. A paint pigment that absorbs blue light and gives o red light 14. An atom is excited when one or more of its electrons is boosted into higher energy levels. 15. Interference colors in a soap bubble give evidence that the soap film has two reflecting surfaces AND is thin (both of these) 16. Atoms can be excited by thermal agitation, electron impact, photon absorption (all of these) 17. Which of the following is not quantized? (all are quantized → energy, radiation, number of people in a room, electric charge) 18. Thomas Youngʹs two-source interference patterns demonstrate the 19. Polarization is a property of transverse waves. 20. The dark lines in the Sunʹs spectrum represent light that is absorbed by the Sunʹs atmosphere. 21. The polarization axes of ordinary sunglasses are vertical (?) 22. The ratio of the energy of a photon to its frequency is Planckʹs constant. 23. The absorption of an infrared photon that excites an atom to emit a green photon violates the law of energy conservation. 24. An emission spectrum is characterized by a set of discrete frequencies. 25. Magenta is seen at one place on a soap bubble film. At a slightly thicker region of the film, one would likely see the color cyan. 26. An object heated to twice the absolute temperature emits radiation with twice the peak frequency. 27. Light from a laser is monochromatic, in phase, coherent (all of these) 28. Two pulses of light, one red and one blue, have the same energy. The pulse with the greater number of photons is the 29. Consider short wavelength plane waves incident upon a barrier with a relatively large opening. Aer passing through the opening, the waves 30. Interference effects are less visible for thick films because the reflected waves 31. The Heisenberg uncertainty principle states that Planckʹs constant sets a limit on accuracy of measurements, we canʹt simultaneously measure exactly both the position and momentum of a particle, we canʹt simultaneously measure exactly a particleʹs energy and time having that energy (all of the above) 32. To say that energy levels in an atom are discrete is to say the energy levels are well defined and separate from one another. 33. Radio waves that diffract more around small buildings are AM. QUIZ 18 1. Beta particles can be stopped by a sheet of aluminum/a thick block of lead (b & c) a. Block of led = need gamma rays b. With a sheet of paper, you can stop ALPHA particles (all would stop alpha; b & c would stop beta; lead would block gamma) 2. An alpha particle is emitted from a nucleus when the probability wave of a cluster of 2 protons and 2 neutrons extends outside the nucleus. a. Neutron turning into a proton emits beta particles 3. The operation of a cloud chamber does NOT rely on polarization a. Guider counter → ionization b. Process order in a cloud chamber: 1) evaporation, 2) ionization, 3) condensation 4. The atomic mass number of an element is the same as the number of its protons and neutrons together = nucleons a. Atomic number - just the number of protons (number on the periodic table) 5. When thorium (A = 90) emits a beta particle, the resulting nucleus has an atomic number [none of these]. Going to be 91 a. When you emit a beta particle, in the nucleus a neutron turns into a proton b. If it emits an ALPHA particle, the atomic number would be 88 i. Alpha particle - helium nucleus (has 2 protons & 2 neutrons) 1. Getting rid of this → lowering the atomic MASS number (would go down by 4 if it emits an alpha) c. If it emits a gamma-ray, then you’re left with 90 (don’t change proton number, so not the atomic number or atomic mass number) QUIZ 19 1. Which of the following is not a factor in determining whether a nucleus is stable (non-radioactive) or unstable (radioactive)? Gravitational force a. 2 forces competing against each other are a strong force & electromagnetic force 2. The half-life on an isotope is two days. At the end of eight days, how much of the isotope remains? One-sixteenth a. After a half life, 50% of the isotope is gone so it keeps splitting 3. Carbon dating could NOT be used to determine the age of a granite statue a. For carbon dating, the thing has to be ALIVE at some point & follow in a certain age range b. Works best from like 50/100 years old to 50k years old c. An adobe brick is made out of straw & plants, so it CAN be carbon dated d. Radioactive dating can be used on all objects, but NOT carbon 4. Most of the radioactivity we personally encounter comes from the natural environment. a. The sun is NOT a source of radioactive exposure, its UV exposure b. Main source of radioactive exposure comes from the ground/earth → uranium decay chain in the earth i. Source of heat for the earth is the CORE, radioactivity decays in the core (what heats/provides heat for the core) → heat conducts to the surface c. Man made radioactivity exposure comes from doctor/medical stuff (not much from nuclear power plants, nor testing of nuclear weapons) d. Fun fact: more people die from wind power production from FALLING off of them, than nuclear 5. Our bodies are able to repair most kinds of molecular damage from radiation if the radiation dose is not too intense a. If it's a little bit at a time, it's not that hard for our bodies to fix b. Smoking sucks in radioactivity into your lungs QUIZ 20 1. A chain reaction grows when the average number of liberated neutrons which go on to cause further fissions is greater than one. 2. Control is exercised in a nuclear reactor by absorbing excess neutrons with control rods. a. What does a moderator do? Slows down fast neutrons i. Fast neutrons gets absorbed by uranium 238 ii. Moderators like water & graphite 3. Fissioning helium would yield a net absorption of energy a. Stuff gets less stable w/ bigger nucleons b. [he also talked a lot during this part and i got a little lost lol] i. Fission means go up the hill [?] c. CHART: high up = protons & neutrons have lots of mass, lower = less mass i. Moving down the hill gives off energy ii. Moving up the hill means you need to create more mass (absorbs energy) iii. Fission ALWAYS moves you to the left (splitting something bigger into smaller pieces) iv. Fusion ALWAYS moves you to the right (takes small things & makes something bigger) 4. Detonation of a fission type atomic bomb is started by pressing together several small pieces of uranium a. Use a fission atomic bomb to set off a fusion bomb 5. Which of the following are characteristics of nuclear fission power plants? 1 kg of fuel produces more energy than 30 freight carloads of coal; release of pollution is vastly reduced compared to fossil fuel plants; waste products are radioactive; risk of releasing large amounts of radioactivity in the case of a major accident [all of these] QUIZ 21 1. According to the special theory of relativity, all laws of nature are the same for the ʹspecialʹ case of reference frames that move at constant velocity. a. General theory of relativity took 15 years for Einstein to discover 2. A spaceship that is traveling very fast with respect to your frame of reference, fires a photon beam that travels at speed c with respect to the spaceship. You measure the photon beamʹs speed to be equal to c. a. C is the speed of light 3. Two lightning bolts are seen to strike two distant locations at the same time. Seen from a different location, the two lightning bolts may or may not be seen at the same time. 4. Compared to standard Earth time, there is a physical slowing of your time when you travel at relativistic speeds AND everyday low speeds (both a & b) 5. Suppose your friend flies by you in a rocket ship traveling at 0.87 c. About how many seconds does your clock advance during the time you see his clock advance 1 second? 2 seconds 𝑡0 a. 𝑡 = 2 1−𝑣 /𝑐 2 QUIZ 22 1. Harry takes a space voyage and returns to find his twin sister has aged more than he has. This is evidence that they have been in different frames of reference, space times, realms of time: (all of the above) 2. Consider a spaceship that moves toward you at 0.5 c (half the speed of light). It fires a probe toward you, relative to itself, at 0.5 c. Relative to you, the probe approaches at about 0.8c. a. 𝑉 = b. 𝑣If1 𝑣1+ 𝑣2 1+ 𝑣1 𝑣2 𝑐 2 = .7 and𝑣1 =.8, then V = 0.96c 3. If I run the 100 m sprint with a speed of 0.98 c, it appears to me that the length of the race is about 20 meters. 2 2 a. 𝐿 = 𝐿0× 1 − (𝑣 /𝑐 ) = 𝐿0/𝛾 4. As the speed of a particle approaches the speed of light, the momentum of the particle approaches infinity. 5. According to special relativity, one can travel at increased rates only forward in time. TEST 4 1. According to relativity theory, if a space trip finds a son or daughter biologically older than his or her parents, then the space trip is taken by the parents. 2. A nuclear power plant is very similar to nuclear bombs, but with more control. 3. According to the special theory of relativity, all laws of nature are the same for the ʹspecialʹ case of reference frames that move at a constant velocity. 4. The operation of a cloud chamber does not rely on polarization. DOES rely on evaporation, ionization, condensation. 5. Our bodies are able to repair most kinds of molecular damage from radiation if the radiation dose is not too intense. 6. Fissioning helium would yield a net absorption of energy. 7. Relativity equations for time, length and momentum hold true for relativistic speeds, everyday low speeds (both of these) 8. Which of the following is not a factor in determining whether a nucleus is stable (non-radioactive) or unstable (radioactive)? Gravitational force 9. The function of graphite in the first atomic reactor was to slow fast neutrons. 10. Two lightning bolts are seen to strike two distant locations at the same time. Seen from a different location, the two lightning bolts may or may not be seen at the same time. 11. The half life of carbon 14 is 5730 years. If a 1 -gram sample of old carbon is 1/8 as radioactive as 1-gram of a current sample, then the age of the old sample is about 17,200 years. 12. Suppose your friend flies by you in a rocket ship traveling at 0.995 c. How many seconds does your clock advance during the time you see his clock advance 1 second? 13. When radium (A = 88) emits an alpha particle, the resulting nucleus has atomic number 86. 14. Detonation of a fission type atomic bomb is started by pressing together several small pieces of uranium. 15. Most of the radioactivity we personally encounter comes from the natural environment. 16. A spaceship that is traveling very fast with respect to your frame of reference, fires a photon beam that travels at speed c with respect to the spaceship. You measure the photon beamʹs speed to be equal to c. (c (speed of light) doesn’t change) 17. If I run the 100 m sprint with a speed of 0.98 c, it appears to me that the length of the race is about 20m. 18. An alpha particle is emitted from a nucleus when the probability wave of a cluster of 2 protons and 2 neutrons extends outside the nucleus. 19. According to special relativity, one can travel at increased rates only forward in time. 20. Different isotopes of an element have different numbers of neutrons. 21. You and a friend share the same space time when there is no relative velocity between you. 22. Which of the following are characteristics of nuclear fusion power plants? No risk of a reactor meltdown accident, virtually no pollution, radioactive or otherwise, a working fusion reactor has not been built yet. 23. Consider a planet at rest and a spaceship that whizzes past the planet at high speed. An observer on the planet sees a contracted spaceship, while an observer on the spaceship sees a contracted planet. (?) 24. Carbon dating could not be used to determine the age of a granite statue. 25. As the speed of a particle approaches the speed of light, the momentum of the particle approaches infinity. 26. A chain reaction grows when the average number of liberated neutrons which go on to cause further fissions is greater than one. 27. Compared to standard Earth time, there is a physical slowing of your time when you travel at relativistic speeds, everyday low speeds (both of these) 28. The atomic mass number of an element is the same as the number of its nucleons. 29. Energy released by the sun results from the process wherein atomic nuclei combine. 30. Which of the following are beneficial applications of radioactivity? Radioactive tracers in crop fertilizer, strong doses of radioactivity for cancer treatment, irradiation of the food supply (all of these) 31. Consider a spaceship that moves toward you at half the speed of light. It fires a probe toward you, relative to itself, at 0.8 the speed of light. Relative to you, the probe approaches at about 0.93 c. 32. Gamma rays can be stopped by a thick block of led. 33. Which radiation has no electric charge associated with it? Gamma rays EXAM: 586703 1. Two charged particles attract each other with a force F. If the charges of both particles are doubled, and the distance between them also doubled, then the force of attraction will be (F/2 F F/4 2F) NONE OF THESE 2. To say that an object is electrically polarized is to say its charges have been rearranged 3. The primary purpose of a lightning rod is to discharge the structure to which it is attached 4. If you use 10 J of work to push 0.5 coulombs of charge into an electric field, its voltage with respect to its starting position is 10 V 5. Electrons are made to flow in a wire when there is a potential difference across its ends 6. A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? more than 20V 7. Most commercial alternating current in North America 60 Hz? 8. The source of electrons lighting an incandescent ac light bulb is atoms in the lightbulb filament 9. The power dissipated in a 4-ohm resistor carrying 3 A is 36 watts 10. As more lamps are put into a series circuit, the overall current in the power source decreases 11. If a steady magnetic field exerts a force on a moving charge, that force is directed at right angles to the direction of the field 12. If we think of the Earth as a magnet, its magnetic north pole is nearest Australia 13. Electromagnetic induction occurs in a coil when there is a change in magnetic field intensity in the coil 14. The secondary of a transformer is the coil connected to the load (primary: input power line) 15. The main difference between a radio wave and a light wave is its wavelength and frequency 16. What is the frequency of an electromagnetic wave that has a wavelength of 30,000 km? __________ 17. Consider light energy that is momentarily absorbed in glass and then re-emitted. Compared to the absorbed light, the frequency of the re-emitted light is the same 18. Earthʹs atmosphere is opaque to waves that are concentrated in the infrared part of the spectrum 19. Compared to its average speed in air, the average speed of a beam of light in glass is less 20. For the same wattage, which lamp provides the most light for nighttime viewing? Sodium vapor light 21. A mixture of magenta and yellow pigments appears red 22. Your image in a plane mirror is virtual 23. The bending of light as it refracts actually shortens the time of travel 24. When a light ray passes, at a non-90 degree angle, from water into glass, it it bends away from the normal (air to water=towards normal) 25. When looking straight ahead at a primary rainbow, you see red light from a given raindrop. To see violet light in the rainbow, you will need to look at a raindrop lower in the sky 26. If a fish in a pond looks upward at 50° to the normal, it will see the ponds bottom 27. Consider long wavelength plane waves incident upon a barrier with a relatively small opening. After passing through the opening, the waves fan out (diffraction) 28. For radio reception, diffraction is helpful (AM frequencies) 29. Thomas Youngʹs two-source interference patterns demonstrate the wave nature of light 30. Interference colors in a soap bubble give evidence that the soap film has two reflecting surfaces and is thin 31. The polarization axes of ordinary sunglasses are vertical 32. An excited atom is an atom has one or more displaced electrons 33. An incandescent spectrum is characterized by (continuous spectrum) all visible colors are present 34. Atoms can be excited by thermal agitation, electron impact, & photon absorption 35. Some light switches glow in the dark after the lights are turned off. This is because of time delay between excitation and de-excitation (aka phosphorus) (none of the above on the other test) 36. The ratio of the energy of a photon to its frequency is Planck's constant 37. Two pulses of light, one red and one blue, have the same energy. The pulse with the greater number of photons is the red pulse 38. If a proton and an electron have identical momenta, the longer wavelength belongs to the both the same 39. Different isotopes of an element have different numbers of neutrons 40. When thorium (A = 90) emits a beta particle, the resulting nucleus has atomic number 41. Carbon dating could not be used to determine the age of 91 42. Which of the following are beneficial applications of radioactivity? radioactive tracers in crop fertilizer, strong doses of radioactivity for cancer treatment, irradiation of the food supply (all of these) 43. Energy released by the sun results from the process wherein atomic nuclei combine 44. Control is exercised in a nuclear reactor by absorbing excess neutrons with control rods 45. Which of the following are characteristics of nuclear fission power plants? 1 kg of fuel produces more energy than 30 freight carloads of coal; release of pollution is vastly reduced compared to fossil fuel plants; waste products are radioactive; risk of releasing large amounts of radioactivity in the case of a major accident [all of these] 46. Event A occurs before event B in a certain frame of reference. In another frame of reference, event A could occur after event b or simultaneous with event b 47. Suppose your friend flies by you in a rocket ship traveling at 0.995 c. How many seconds does your clock advance during the time you see his clock advance 1 second? 10 seconds 48. Harry takes a space voyage and returns to find his twin sister has aged more than he has. This is evidence that they have been in different frames of reference, space time, & realms of time 49. Consider a spaceship that moves toward you at 0.4 c (four-tenths the speed of light). It fires a missile toward you, relative to itself, at 0.5 c. Relative to you, the missile approaches at about 0.75 c 50. Consider a planet at rest and a spaceship that whizzes past the planet at high speed. An observer on the planet sees a contracted spaceship, while an observer on the spaceship sees contracted planet