Reflection and refraction of light Mirrors and lenses

1. Reflection and refraction of lightMirrors and lenses

3. Ch 22: Reflection and refraction • Reflection –part of the light encountering the second medium bounces off that medium

4. Refraction- the light is passing into the second medium bends through an angle with respect to the normal to the boundary

5. Reflection of light: -specular reflection -diffuse reflection • Normal- a line perpendicular to the surface

6. v • Refraction sinθf/sinθi=v2/v1=ct • The path of a light ray through a refracting surface is reversible

7. The Law of Refraction • The index of refraction is a ration n=c/v • n= speed of light in vacuum/ speed of light in a medium • As light travels from one medium to another, its frequency doesn’t change. v= f λ λ1/λ2=v1/v2=(c/n1)/(c/n2)=n2/n1 λ1n1=λ2n2 • Snell’s law of refraction: n1sinθ1=n2sinθ2

8. Dispersion and Prisms • Dispersion – the dependence of the index of refraction on a wavelength • Snell: the angle of refraction made when light enters a material depends on the wavelength of the light

11. Total internal reflection

12. Total internal reflection occur when light encounters the boundary between a medium with a higher index of refraction and one with a lower index of refraction • Critical angle: θ2=90o n1>n2: sinθc=n2/n1

14. Ch 23: Mirrors and Lenses • Consider a point source of light (object), after reflection, the rays diverge , but they appear to the viewer to come from a point behind a mirror (image)

15. Images are formed at the point where rays of light actually intersect or where they appear to originate • p- object distance; • q-image distance; -Real image- light asses through the image point -Virtual image- light doesn’t pass through the image point but appears to come (diverge) from there

16. The image formed by an object placed in front of a flat mirror is as far behind the mirror as the object is in the front of the mirror • the object height h = the image height h’ • The lateral magnification (def): • M=h’/h =the image height/ the object height

17. Mirror properties: • The image is as far behind the mirror as the object is in the front • The image is unmagnified, virtual and upright

18. Spherical mirrors:

19. Concave mirrors

20. M=h’/h =-q/p • Mirror equation: • 1/p + 1/q =2/ R • f=R/2 → 1/p +1/q =1/f (q- image distance; p- object distance, R-radius of curvarture)

21. Convex mirrors (divergin mirrors)

24. Ray diagrams for mirrors: • 1. Rays 1 is parallel to the principal axis and is reflected back through the focal point • 2. Ray 2 is drawn through the focal point and is reflected parallel to the principal axis • 3. Ray 3 is drawn through the center of curvature, C, and is reflected back on itself

26. Flat Refracting surfaces: • n1/p=-n2/q • q=- (n2/n1)p • The image formed by a flat refracting surface is on the same side of the surface as the object

27. Thin lenses: converging lenses and diverging lenses

29. M=hi/ho=-q/p • tanθ=AC/f → tan θ=-hi/q-f • ho/f =-hi/q-f → q/p =q-f/f → 1/p +1/q =1/f –thin lenses equation • 1/f=(n-1)(1/R1 – 1/R2) –lens maker’s equation

33. Combination of thin lenses: