1. Ch. 17 Reflection and Refraction
Milbank High School

2. Sec. 17.1 How Light Behaves at a Boundary
Objectives
Explain the law of reflection
Distinguish between diffuse and regular reflection and provide examples
Calculate the index of refraction in a medium

3. The Law of Reflection Smooth Surfaces Seemingly smooth surfaces
Mirrors
Angle of incidence = angle of reflection
Seemingly smooth surfaces
Walls
Paper
Actually rough surfaces
Light waves result in diffuse reflection

4. Refraction of Light Refraction
Change in direction or bending of light at the boundary of two media
Plastics, glass
Optically dense materials
If angle of refraction is smaller than the angle of incidence

5. Snell’s Law
The degree of refraction depends on angle of incidence and properties of the medium
Snell’s Law
Ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant

6. Index of Refraction and the Speed of Light
Measure of how much light bends in a new medium
It bends because of a change in speed
nsubstance = c/vsubstance

7. Review Questions Could the index of refraction ever be less that 1?
What behaviors does light exhibit?

8. Sec. 17.2 Applications of Reflected and Refracted Light
Objectives
Explain total internal reflection
Define the critical angle
Explain effects caused by the refraction of light in a medium with varying refractive indices
Explain dispersion of light in terms of the index of refraction

9. Total Internal Reflection
Occurs when light passes from a more optically dense medium to a less optically dense medium at an angle so great that there is no refracted ray
Critical angle
The incident angle that causes the refracted ray to lie right along the boundary of the substance, angle Θc
sin Θc = nr/ni

10. Effects of Refraction Mirages Sunlight after the sun has set
Index of refraction changes in hot air vs. cool air
Sunlight after the sun has set
Index of refraction changes due to the change in density of the atmosphere

11. Dispersion of Light Separation of light into its spectrum
Happens as light travels through a prism
Glass
Diamonds
Water
Red bent the least
Violet bent the most

12. Rainbows
Spectrum formed when sunlight is dispersed by water droplets in the atmosphere
In afternoon, only see rainbows to the east