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Geometric Optics

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Geometric Optics

1. 1. Geometric Optics Sarah & Emma
2. 2. i. Law of Reflection• Angle of incidence = angle of reflection• Incident ray, reflected ray and normal line all lie on same plane
3. 3. Mirror Reflected rayNormal line Incident ray Object Angles of incidence Angles of refraction Source: ppt
4. 4. Specular vs. Diffuse reflection• Specular reflection – reflection off smooth surface (i.e. mirror)• Diffuse reflection – reflection off rough surfaces (i.e. asphalt)
5. 5. • A rough surface diffuses light because every individual light ray hits a point of the surface that is oriented at a different angle. This means they will reflect at all different angles.• Source: http://www.physicsclassroom.com/class/refln/U13L1d.cfm
6. 6. ii. Refraction• Bending of light – light bends when it passes from one medium to another• The boundaries where refraction takes place are called interfaces Glass interfaces Light
7. 7. nglass=speed of light in vacuum/ speed of light in glass≈speed of light in air/speed of light in glass• These two “index of refraction”s are the same to 3 sig figs
8. 8. Snell’s Law• For a given substance, the ratio sin(angle of incidence)/sin(angle of refraction) is a constant Angle of incidence (θair) Angle of refraction (θglass) Normal line Light
9. 9. Angle of incidence (θair) Angle of refraction (θglass) Normal line Lightnglass = sinθvacuum/sinθglass = vvacuum/vglass≈ sinθair/sinθglass = vair/vglass
10. 10. • If we add a substance other than air (glass & water instead of air & water)… θglass Glass Water θwater• nXsinθX = nysinθy= nzsinθz = … as long as the interfaces are parallel
11. 11. • The denser the substance, the greater the index of refraction• As light goes from less dense to denser, it bends toward the normal (angle of incidence > angle of refraction)• As light goes from denser to less dense, it bends away from normal (angle of incidence < angle of refraction)
12. 12. iii. Prism• Dispersion – separation of visible light into its different colors• Angle of deviation –overall refraction caused by passage of light ray through prism
13. 13. Dispersion• Different colored lights have different frequencies• Therefore they travel through material w/ different speeds• This leads to different angles of refraction and the dispersion of light
14. 14. Deviation• Angle of deviation – angle b/w incident ray and refracted ray that leaves prism θblue θred