Chapter 17Chapter 17Reflection and RefractionReflection and Refraction

Ch 17.1 Ch 17.1

How light behaves at a How light behaves at a boundaryboundary

I How light behaves at a boundaryI How light behaves at a boundary

A. The law of reflectionA. The law of reflection

B. The refraction of lightB. The refraction of light

C. Snell’s lawC. Snell’s law

D. Index of refraction and the Speed of D. Index of refraction and the Speed of lightlight

A. Law of ReflectionA. Law of Reflection

Regular reflectionRegular reflection

Diffuse reflectionDiffuse reflection

B. Refraction of LightB. Refraction of Light

Bending of light at a boundaryBending of light at a boundary

Angle of refractionAngle of refraction

Optical densityOptical density

C. Snell’s lawC. Snell’s law

The ratio of the sine of the angle of The ratio of the sine of the angle of incidence to the sine of the angle of incidence to the sine of the angle of refraction is a constant.refraction is a constant.

Index of refractionIndex of refraction

n = sin θn = sin θii /sin θ /sin θr r

Snell’s lawSnell’s law

nnii sin θ sin θii = n = nrr sin θ sin θrr

PSSPSS

Drawing ray diagramsDrawing ray diagrams1.1. Draw a diagram showing the two media.Draw a diagram showing the two media.2.2. Label the media and indicate the two Label the media and indicate the two

indices of refraction indices of refraction 3.3. Draw the incident ray to the point where Draw the incident ray to the point where

it hits the surface, then draw a normal to it hits the surface, then draw a normal to the surface at that point.the surface at that point.

4.4. Use a protractor to measure the angle of Use a protractor to measure the angle of incidence.incidence.

5.5. Use Snell’s law to calculate the angle of Use Snell’s law to calculate the angle of refractionrefraction

6.6. Use a protractor to draw the refracted ray Use a protractor to draw the refracted ray leaving the surface at the point where the leaving the surface at the point where the incident ray entered.incident ray entered.

7.7. Evaluate your work.Evaluate your work.

Index of Refraction and the Index of Refraction and the Speed of lightSpeed of light

Recall that when a wave moves from one Recall that when a wave moves from one medium to another where the wave speed medium to another where the wave speed is different, the frequency does not is different, the frequency does not change.change.

v v = = ffmaterial = vmaterial/f

Index of refractionnsubstance = c/vsubstance

Homework: Homework:

– Chapter 17 review problemsChapter 17 review problems