1. THIN LENSES Refraction

2. What Is Love Light? Isaac Newton believed light to be a ray of corpuscles (particles), because light travels in a straight line (think inertia!) Robert Hooke believed light to have the wave-like nature Newton’s idea prevailed… until over a century after his death…

3. LIGHT INTERFERES thus it’s a WAVE! 1801 – Thomas Young produces interference of light

4. Speed of light is finite, constant… In vacuum, that is… Light is a(n) ______________ wave It ____________ a medium In any substance (anything other than vacuum) light slows down… and its rays bend

5. Light travels through materials at a speed less than its speed in vacuum. DEFINITION OF THE INDEX OF REFRACTION The index of refraction of a material is the ratio of the speed of light in a vacuum to the speed of light in the material:

6. n r > n i (faster to slower!)

7. n r < n i (slower to faster)

10. SNELL ’ S LAW OF REFRACTION When light travels from a material with one index of refraction to a material with a different index of refraction, the angle of incidence is related to the angle of refraction by SNELL ’ S LAW

11. Example 1 Determining the Angle of Refraction A light ray strikes an air/water surface at an angle of 46 degrees with respect to the normal. Find the angle of refraction when the direction of the ray is (a) from air to water and (b) from water to air.

12. LAB Determine the index of refraction of a certain plastic Materials:

13. Internal Reflection

14. When light passes from a medium of larger refractive index into one of smaller refractive index, the refracted ray bends away from the normal. Critical angle

15. Find critical angle for 1) diamond 2) water 3) ice

16. LAB 2 Calculate critical angle and check it experimentally Materials: