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We will land, in the sun Reflection - Reflection is when light changes direction by bouncing off asurface. * When light is reflected off a mirror, it hits the mirror at thesame angle (i, the incidence angle) as it reflects off the mirror (6r, the reflection angle). * The normal is an imaginary line which lies at right angles to the mirror where the ray hits it. Law of Reflection: Equal Angles of Reflection Angle of Angle of Incidence | Reflection 1. Angle of Incidence is always equal to the Angle of Reflection. 2. The Incident Ray, the Normal Ray and the Reflected Ray all lies in thesame plane at the point of incidence. Types of Reflection: Specular (Regular)Reflection — occurs only on smooth surfaces such as glass, Speaular Reflection woods, mirror, mercury wheremost of the energy is reflected reflected rays travel in the (smooth surfaces) same direction. Diffuse (Irregular) Reflection — occurs on rough and uneven surface like where most of the energy is absorbed - reflected rays spread out in different directions Diffuse Reflection Reflection in Spherical Mirror Cardinal Points -— The rays are controlled by a number of cardinal points: * (Principallaxisi(P)— line passing through the center of the sphere and attaching to the mirror in the exact center of a mirror - @enteroficurvaturen(e) — the point in the center of sphere from which the ‘mirror was sliced *@Vertex(V)»— the point on the mirror’s surface where the principal axis” ‘meets the mirror * focal point (F) — Usable Rays in Construction of Images by Ray Method: Ray #1- ray parallel to principal axis passes through (f) after reflection incident ray P C Vv a Ray #2- ray passing through (f) will be reflected parallel to the principal axis incident ray P C V reflected ray Ray # 3- ray passing through (C) will be reflected Ray #4- ray incident to the vertex of the mirror will be reflected according to the laws of reflection CASE 4- CONCAVE MIRRORS: OBJECT INFRONT OF (F) — The image formed when an object is placed infront of (f) is located behind the mirror. — It is a virtual, upright image that is larger in size than the object. - It is virtual since it is formed only where light rays seem to be diverging from. [ ea CASE 5- CONCAVE MIRRORS: OBJECT AT (C) — The image wil be formed at (C) also, but it will be inverted. — It will be real and the same size as the object. OBJECT IMAGE CASE 6 - CONCAVE MIRRORS: OBJECT AT (F) — No image will be formed. = ll rays will reflect parallel to the principal axis and will never converge. — The image is “at infinity.” Cc | Images Produced by Convex Mirrors — fi convex mirror has the same basic properties as a concave mirror but its focus and center are located behind the mirror. — This means a convex mirror has a negative focal length (used later in the mirror equation). — Light rays reflected from convex mirrors always diverge, So only virtual images wil be formed. — Rays parallel to the principal axis wil reflect as if coming from the focus behind the mirror. — Rays approaching the mirror on a path toward (f) will reflect parallel to the principal axis. - The image formed by a convex mirror no matter where the object is placed will be virtual, upright, and smaller than the object. As the object is moved closer to the mirror, the image will approach the size of the object. Lens & Mirror Equation Ti ff [p ie Where: f =focallength p=object distance q= image distance f- is negative for diverging mirrors and lenses q- is negative when the image is behind the lens or mirror Mirror Sign Convention Di + for real image — for virtual image f + for concave mirrors — for convex mirrors Refraction — Bending of light as it goes from one medium to another of different density. -— Abrupt change of the velocity of light ray when it travels from one medium to another medium. — Suppose light comes from air, which in this case will be considered to be a vacuum, Strikes a boundary at some angle of incidence measured from a normal line, and goes into water. _ Speed of Light in a Vacuum — ¢ " Speed of Light in a medium Vm — The ratio of the two speeds can be compared. — The denominator in this case will ALWAYS be smaller and produce a unitless value greater or equal to 1. This value is called the new medium’s INDEX OFREFRACTION (n). Boundary Speed og lignt _ 1X4, 000 milgee “An a medium Irv = 13H, TH4. VW mileee Ql one I$l4,000 milsec > 1-10 10% Az miler Index of Refraction Types of Index of Refraction: * Absoluteindex ofrefraction — ratio of the speed of light in empty space or vacuum (air) to the speed of light in some other optical medium * Relativeindex ofrefraction — ratio of the speed of light of two optical media, of which neither is air (or when such is the case that light does not originate from air). Refraction is based on the idea that LIGHT is passing through one MEDIUM into another. What EXACTLY is light doing when it reaches a new medium? ne - Some of the light REFLECTS off the boundary and betdent em ee ecedny some of the light REFRACTS through the boundary. a NE — Angle of incidence = Angle of Reflection = setae - fingle of Incidence > or < the Angle of refraction hes depending on the direction of the light Laws of Refraction Lossy — 4 ray of light striking a refracting surface perpendicularly is undeviated. -— fi ray of light which passes obliquely from a rawar medium of lesser to one of greater optical ane density, is bent toward the normal (decrease in speed) - fi ray of light which passes obliquely from a denser to a rarer medium is bent away the Spree normal. (increase in speed) — — The incident ray, normal and refracted ray, t~#* all lie in the same plane at the point of incidence Law 45 Shallowing Efiect of Refraction ran n q- apparent distance of object (image) n'— index of refraction in which the eye is located p- actual distance of object n- index in which object is located 1. a Le 2. 290 wes 4 x= i ILS Lap 1% Y —,INOHm™ ich = < sd we \ rs Tech | YY : AV 1n0 1 si ia P= 243.16 m %= Lum Critical Angle Necsreone ne - Angle of incidence at which the angle of refraction makes an angle of 90 degrees with the normal - Angle of incidence, which just transmit a ray of light in a dense medium to pass out into a rare medium. Light Ray Formula: n sin(i) = n' sin(R) / n sin (i) = n° sing0 Nsinti) = 1 sin Cay 1. Nes sintid = 1 sinay 7) Us sel sn = 00-4040 Bi = 37-31" Total Internal Reflection - When the incident ray coming from a dense medium subtends an angle with the normal to the refracting surface, greater than the critical angle for the Substance, it does not pass out into the rare medium but suffers Internal reflection | 
