1. Chapter 15: Refraction

2. Refraction refraction: the bending of a wave as it moves from
one medium to another
wavefronts
f is constant, so as v
changes the l must
change (must change
direction)
faster
slower
Waves bend toward the normal when they slow down!

3. Sound Refraction
Sound bends toward cooler air (they slow down) so you can hear more clearly across a lake at night.

4. Light Refraction Objects appear to be more shallow in water.
soda appears
to be at edge
of bottle

5. Index of Refraction Index of Refraction (n) How fast does light travel
through water?

6. Snell’s Law Snell’s Law q1 n1 A ray of light incident in air at 45o
refracts at 32o when it enters
another medium. What is the
index of the second medium? n2 q2

7. Objectives Understand how lenses converge or diverge light rays.
Be able to draw ray diagrams for lenses.
Be able to do “lens math.”

8. Lenses (from lentils) Lenses can converge or diverge light.
Lenses produce images just like mirrors (but w/ chromatic aberrations)
The mirror equations can be used to do lens math.
+ F F

9. Some Ray Diagrams

10. Lens Math
A 12.4 cm tall candle is placed 16.3 cm from a convex lens with a 25.0 cm focal length.
Calculate the image distance, the magnification, and the image height. Describe the image.

11. Objectives Know the parts of the eye.
Be able to explain how eyeglass lenses can be used to correct hyperopia and myopia.
Understand how a telescope or microscope produces an inverted and enlarged virtual image

12. The Eye

13. The Eye

14. Corrective Lenses
Hypermetropia (far-sightedness) is corrected with a convex lens.
Myopia (near-sightedness) is corrected with a concave lens.

15. Refracting Telescope The eyepiece lens magnifies the real
image produced by the
objective lens.

16. Objectives
Understand the process of total internal reflection and how it relates to refraction.
Understand how refraction leads to atmospheric phenomena like mirages and rainbows.

17. Total Internal Reflection

18. Total Internal Reflection
What is qC for
water (1.33) into air
(1.00)?

19. Atmospheric Refraction: Mirages
object
Light refracts
away from N
in warmer air
(speeds up). qC
warmer air
image

20. Dispersion dispersion by a prism: the
index of refraction varies with wavelength (so blue refracts more than red)

21. Rainbows Light disperses as it refracts, internally
reflects, and refracts again.
The different colors are
arranged in a circle between
40o and 42o relative to the
anti-solar point or antisun.