Principles of Physics

Change in direction of light as it moves into a new medium and speed changes Only occurs if light enters medium such that 0˚< θ i < 90˚ θiθi θrθr θ r = angle of refraction

Refraction can only occur when: there is a medium change the light enters at an angle between 0˚ and 90˚ When a toy car goes from tile to carpet such that both front wheels hit the carpet at the same time, the whole car slows down at the same time. A change in direction does not occur. When a toy car goes from tile to carpet at an angle. Each wheel hits the carpet at a different time. The first wheel to hit the carpet, slows down before the others causing the car to turn toward it.

90˚ 1.To measure the angle place the protractor on the normal line facing the ray 2.Measure the angle from the normal line to that ray θiθi

90˚ 1.To measure the angle place the protractor on the normal line facing the ray 2.Measure the angle from the normal line to that ray θrθr

Determine the incident and refracted angles

Ratio of the speed of light in a vacuum to the speed of light in other materials n= index of refraction (unitless) c = speed of light in a vacuum v = speed of light in material Greater n more the light slows down in the material

Determine the speed of light in water if the index of refraction for water is 1.33

Relates the index of refraction to the angle of refraction Dont forget ˚ is a unit!!!

MaterialIndex Vacuum1 Air at STP Ice1.31 Water at 20 C1.33 Crown glass1.52 Salt1.54 Flint glasses1.66 Sapphire1.77 Diamond2.417 Corn oil1.47 Lucite1.5

Determine the angle of refraction. n 1 = n air = 1.00 n 2 = n glass = 1.52 θ i = 30˚ θrθr crown glass θ 2 19˚

θ c =critical angle: incident angle that causes refracted angle to be 90˚ in air

Transparent materials can reflect. Total Internal Reflection: n high to n low θ i > θ c i ii θ i = θ r

All wavelengths of light travel at 3x10 8 m/s in a vacuum In other materials each wavelength travels at a different speed In most materials red travels fastest and violet travels slowest Red is refracted least and violet is refracted most therefore the colors separate