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1402Lab6 - Reflection and Refraction Theory Whenever a wave...

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Reflection and Refraction Theory: Whenever a wave traveling in some medium encounters an interface or boundary with another medium either (or both) of the processes of (1) reflection and (2) refraction may occur if the speed of the wave is different in the two media. If the wave being considered is light the speed of light in any medium is characterized by the index of refraction for the medium, n, where n c/v [1] where c is the speed of light in a vacuum, and v is the speed of light in the medium. (Note that for a vacuum or air n=1.00.) Reflection In reflection, a ray of light traveling in a straight line in medium 1 encounters an interface with medium 2 and the incident ray is reflected (or bounced) backed into medium 1 at the interface of the two media as depicted in Figure 8 – 1. θ r θ i medium 1 Normal medium 2 Figure 8 –1 The normal is a reference point which is always perpendicular to the surface at the “point of impact” where the light is incident onto the surface. If the ray incident on the interface makes an angle θ i with the normal to the surface at the “point of impact” on the interface, the reflected ray will make an angle θ r with the normal from the “point of impact” equal to the incident angle θ i . The relationship between the angles θ i and θ r for all reflections is called the Law of reflection which can be stated in two parts: 1. θ i = θ r , and 2. θ i and θ r are coplanar, (i.e. lie in the same plane.) [2] For light parallel to the principal axis and incident on a spherical (or cylindrical) surface with a radius R, the reflected light will cross the principal axis at a focal point, f, from the vertex (see Figure 8-2) such that f = R/2 [3]
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