SNC2D - Academic Science - Physics Optics Notes

SNC2D Grade 10 Academic Science – Physics Optics Notes SNC2D Optics Review Light -is energy -made of light particles called photons -an electromagnetic wave -travels at a very high speed -travels in a straight line -does not need medium to be transmitted -properties of particles and EM wave (particle-wave duality) -study of light: OPTICS Medium: any physical substance through which energy can be transferred Radiation: method of energy transfer that does not require a medium, the energy travels at speed of light Visible L i g h t : E M w a v e s t h a t t h e h u m a n e y e c a n s e e Electromagnetic Wave -a wave that has both electric and magnetic parts -does not require medium -travels at the speed of light -use electromagnetic spectrum to classify these light waves -visible spectrum is the continuous sequence of colors that make up white light -color sequence is the order of the rainbow (ROYGBIV, red being lower energy and increasing towards violet) – lowest highest energy : r a d i o w a v e s , m i c r o w a v e s , infrared light , v i s i b l e l i g h t , U V l i g h t , x – r a y s , gamma rays Sources of Light Indirect Light: non-luminous objects reflect luminous object’s light (ex. moon) Direct Light: luminous objects produce their own light (ex. sun) Types of Light Incandescent: heated materials produce light (ex. lightbulb, molten metals, stove element) Electrical Discharge: electrical current flowing through gas produces light (lightning, northern lights) Phosphorescent: materials called ‘phosphors’ absorb UV light from surroundings, STORE IT, emit energy as visible light (ex. glow in the dark toys) Fluorescent: materials absorb UV light then IMMEDIATELY release it as visible light Chemiluminescence: mixture of chemicals produce light (ex. glow sticks) Bioluminescence: chemiluminescence in living organisms (ex. jellyfish, e.coli, fireflies) Triboluminescence: light produced by friction (ex. lifesavers) LED (light emitting diode): electrical current flows through semiconductors (ex. new Christmas lights) The Ray Model -light travels in a straight line -light rays are the direction and straight path of the light -using light rays to see the path of light is called geometric optics -matter can be transparent (see behind clearly), translucent (some light passes, can’t see behind clearly), or opaque (no light passes, matter absorbs light) Reflection -the bouncing back of light from any surface Images: a reproduction of an object through the use of light Mirror: a ny polished surface reflecting an image (has two parts:glass/reflective surface and reflective thin film/opaque side) Plane : f l a t Incident Ray: incoming ray that strikes the surface Reflected Ray: ray that bounces off reflective surface Normal: line perpendicular (90 degrees) to the mirror’s surface Angle of Incidence: angle between incident ray and normal Angle of Reflection: angle between normal and reflected ray Laws of Reflection 1. The angle of incidence EQUALS the angle of reflection 2. The incident ray, reflected ray, and the normal all lie on the same plane Specular Reflection: -reflection on smooth shiny surface -series of parallel rays hit the surface, their reflected rays are also parallel Diffuse Reflection: -light shines on surface that is not perfectly flat -many incident rays and angles of incidence reflected rays are also different A virtual image is one that is created by light from an apparent light source; it cannot be projected on a screen because light does not arrive at or originate from the actual image location. Images in Plane Mirrors -use the laws of reflection -distance from object to mirror is same as distance from image to mirror (image is located at same distance but reversed) -object-image line is perpendicular to the mirror surface -extrapolate the rays of light from the eye -image is flipped horizontally and is in reverse order -this is called LATERAL INVERSION (180 degree rotation of an object) Properties of an Image SALT S: size of image (compared to object: same, smaller, larger) A: attitude of image (orientation compared to object: upright, inverted, laterally inverted L: location of image T: type of image; virtual, real Centre of Curvature (C): center of the sphere whose surface forms the mirror Principal Axis: line going through the center of curvature and the center of the mirror Vertex (V): point where the principal axis intersects the mirror Focus (F): the single point where all light rays parallel to the principal axis will be reflected off the mirror Concave Mirror (converging) -caves you in; inner surface/center of mirror bulges away from you Concave Mirror Rules: 1. Any ray traveling parallel to the principal axis is reflected through the focal point (STRAIGHT AND “F”) 2. Any ray traveling through the focal point (F) is reflected parallel to the principal axis ( “F” AND STRAIGHT) 3. Any ray traveling through the center of curvature (C) is reflected back through the center of curvature (THROUGH “C”) Converging/Concave Mirrors Object Image Location Size Attitude Location Type beyond C smaller inverted between C and F real at C same size inverted at C real between C and F larger inverted beyond C real at F no image no image no image no image inside F larger upright behind mirror virtual Same rules as Concave Mirrors 1. STRAIGHT AND “F” 2. “F” AND STRAIGHT 3. THROUGH “C” Focus (F) and center of curvature (C) is now behind the mirror as the VIRTUAL FOCUS Convex Mirrors (Diverging) -brain extrapolates the rays behind the mirror, where they appear to converge THE REFLECTED RAY CONTINUES BEHIND THE MIRROR AS A DOTTED LINE IMAGE IS ALWAYS UPRIGHT, SMALLER, BEHIND THE MIRROR, VIRTUAL Refraction -happens between 2 media/materials -light bends when it travels from one material into another Angle of refraction: the angle between refracted ray and the normal Rules for Refraction 1. Incident ray, refracted ray , and normal all lie on the same plane-incident and refracted ray are on opposite sides of the line that separates the two media 2. Light bends TOWARDS the normal when the speed of light in the second medium DECREASES 3. Light bends AWAY from the normal when the speed of light in the second medium INCREASES Index of Refraction -the ratio of the speed of light in a vacuum to the speed of that medium 8 -Light travels the fastest in a vacuum [3.00×10 ] -Mediums slow down light because it contains higher index of refraction v = speed of light in given medium c = speed of light in vacuum n = index of refraction N=C/V -index of refraction can also be calculated using the sines of the angles: N=SIN