1. Announcements Homework for tomorrow…
(Ch. 23, CQ6, Probs. 16, 18, & 53)
23.4: 5.4 m
23.8: 42°
23.10: 35°
Office hours…
MW 12:30-1:30 pm
TR am
F am
Tutorial Learning Center (TLC) hours:
M 8-1 pm, 3-6 pm, W 8-1 pm, 2-6 pm
TR 8-6 pm, F 8-2 pm

2. Ray Optics (Image Formation by Refraction & Color and Dispersion)
Chapter 23
Ray Optics
(Image Formation by Refraction &
Color and Dispersion)

3. Last time… Snell’s Law is…
Critical Angle, θc, for Total Internal Reflection…

4. 23.4: Image Formation by Refraction
Q: If you see a fish that appears to be swimming close to the front of an aquarium, but then look through the side, you’ll find that the fish is actually farther than you thought.
Why?

5. 23.4: Image Formation by Refraction
Q: If you see a fish that appears to be swimming close to the front of an aquarium, but then look through the side, you’ll find that the fish is actually farther than you thought.
Why?
A: Refraction of light at the boundary!

6. 23.4: Image Formation by Refraction
What is the image distance, s’, in terms of the object distance, s, as measured from the boundary?

7. 23.4: Image Formation by Refraction
What is the image distance, s’, in terms of the object distance, s, as measured from the boundary?
Notice:
n2 is the index of refraction of the material that the light ray is transmitted into.

8. Quiz Question 1
A fish in an aquarium with flat sides looks out at a hungry cat. To the fish, the distance to the cat appears to be
less than the actual distance.
equal to the actual distance.
more than the actual distance.

9. i.e. 23.6 An air bubble in a window
A fish and a sailor look at each other through a 5.0 cm thick glass porthole in a submarine. There happens to be an air bubble right in the center of the glass.
How far behind the surface of the glass does the air bubble appear to the fish? To the sailor?

10. 23.5 Color and Dispersion
Color is a perception, NOT a physical quantity!
A prism disperses white light into various colors.
When a particular color of light enters a prism, its color does NOT change.

11. 23.5 Color and Dispersion
Different colors are associated with light of different wavelengths.
The longest wavelengths are perceived as red light; the shortest as violet light.
What we perceive as white light is a mixture of all colors.

12. Dispersion…
…is the slight variation of index of refraction with wavelength.
Below is the dispersion curves of two common glasses.
Notice:
n is larger when the wavelength is shorter.

13. Dispersion…
…is the slight variation of index of refraction with wavelength.
Below is the dispersion curves of two common glasses.
Notice:
n is larger when the wavelength is shorter.
Q: Which color travels faster (in the material)?

14. Dispersion…
…is the slight variation of index of refraction with wavelength.
Below is the dispersion curves of two common glasses.
Notice:
n is larger when the wavelength is shorter.
Q: Which color travels faster (in the material)?
Q: Which color refracts more?

15. Rainbows…
The basic cause of the rainbow is a combination of refraction, reflection, and dispersion.

16. Rainbows…
A ray of red light reaching your eye comes from a drop higher in the sky than a ray of violet light.
You have to look higher in the sky to see the red light than to see the violet light.

17. Quiz Question 2
A narrow beam of white light is incident at an angle on a piece of flint glass. As the light refracts into the glass,
It forms a slightly diverging cone with red rays on top, violet rays on bottom.
It forms a slightly diverging cone with violet rays on top, red rays on bottom.
It remains a narrow beam of white light because all the colors of white were already traveling in the same direction.

18. Colored Filters and Colored Objects
Green glass is green because it absorbs any light that is “not green.”
If a green filter and a red filter are overlapped, no light gets through.
The green filter transmits only green light, which is then absorbed by the red filter because it is “not red.”

19. Colored Filters and Colored Objects
The figure shows the absorption curve of chlorophyll, which is essential for photosynthesis in green plants.
The chemical reactions of photosynthesis absorb red light and blue/violet light from sunlight and puts it to use.
When you look at the green leaves on a tree, you’re seeing the light that was reflected.