1. refraction When a ray of light traveling through a transparent medium encounters a boundary leading into another transparent medium part of the ray is reflected and part enters the second medium is refracted.. v1 is the speed of light in medium 1. v2 is the speed of light in medium 2.

2. Light rays behavior through medium

3. The law of Refractive index When light passes from one transparent medium to another, it’s refracted because the speed of light is different in the two media. The index of refraction, n, of a medium is defined as the ratio c/v ; As light travels from one medium to another, its frequency doesn’t change. Therefore, because the relationship ν=f λ must be valid in both media and because f1 = f 2= f, we see that v1 = λ1 f and v2= λ2 f

5. Huygens’ Principle Applied to Refraction

6. ■ Quick Quiz: A material has an index of refraction that increases continuously from top to bottom. Of the three paths shown in Figure 22.10, which path will a light ray follow as it passes through the material? ?

7. Optical path The path d of a ray of light in any medium is given by the product velocity in time : d= vt Since by definition n=c/v, which gives v=c/n, we can write nd=ct or d= c t n The product nd is called the optical path Δ: Δ=nd If a light ray travels through a series of optical media which thickness are d1,d2,d3……and refractive indexes are n1,n2,n3…….the total optical path is: Δ=n1d1+n2d2+n3d3+…….. n1n2n3 Path in medium d1d2 d3

9. x y’y’ x’x’ y n1 n2 n1 θ θ1 α α1 δ D b c g e a d The relationship between the incident and outer ray bounded media by two parallel surface from a Sinθ = Sin θ1 So, θ = θ1 ray Angle of Incident Angle of outer ray We find that ab and cd rays are parallel and have perpendicular displacement which depend on thickness δ. δ= bc Sin(θ-α) = D Sin(θ-α) Cosα

10. total internal reflection can occur when light encounters the boundary between a medium with a higher index of refraction and lower index of refraction. Total internal reflection and the critical angle

12. Total internal reflection Fiber optics