1. Tuesday, March 26, 2013
Warm-Up!
On a separate sheet of paper, please write out the following questions and answers (see sections & 27.5, pages ):
What does it mean to say that light is "incident" upon a material?
When light is incident upon a material, what are the three (3) different things (paths) it could do?
Does a combination of all three ever occur?
You will turn this paper in at the end of class.

2. Warm-Up answers:
1. Incident = rays of light hit the object at a specific angle and different results occur.
2. 3 different behaviors/paths:
a. reflect/bounce off
b. absorbed by the material
c. it can be transmitted through (transparency)
3. Usually, some combination of all three occurs.

3. Reminders:
If you didn't turn in yesterday's assignment, see the white board and be sure you turn it in today.
Lab activity tomorrow.
You will write some notes on the same paper as today's Warm-Up activity, so keep that handy and be prepared to turn it in.

4. Review Questions #7-24, 39, 41 (pgs. 401-402
Assigned Monday, March 18
4 points possible
7. a. 340 m/s b. Sound travels faster at higher
temperatures.
8. Faster in water, and faster again in steel.
9. The atoms are closer together, and solids and
liquids are more elastic mediums.
10.More surface is forced to vibrate and push more
air.
11. They have different natural frequencies.

5. 12. The frequency is characteristic of the object's
shape, size and composition.
13. Resonance is forced vibration at the natural
frequency.
14. Tissue paper has no natural frequency.
15. By input of vibrations at a frequency that
matches the natural frequency of the object.
16. The circuit in the radio is adjusted to resonate
with the broadcast frequency.
17. Yes, it is destructive interference.

6. 18. The crests of one coincide with the troughs of
the other.
19. Beats are a result of periodic interference.
20. ( )Hz = 2-Hz
21. Light travels faster than sound.
22. There is a time delay for sound from a marching
band near the front of a long parade to reach the marchers at the end.
m (sound delay was 1s, and v-340 m/s,
so d = 340 m).

7. 24. Distant sound should get to you after you
see the light. Also, sound cannot travel in a vacuum.
39. Yes. v = 340 m/s = km/s
d = vt = (0.333 km/s)(# of seconds)
41. The pitch of the sound can be changed by
adding water to the bottle or by using a bottle of a different depth.
You could use a series of bottles to get the same sound effect.

9. Light and Transparent Materials
When light passes through something (transparent material), the atoms within the material absorbs the energy and immediately re- emits it as light.
The electrons in the matter are forced into vibration that depends on the frequency of the light and the natural frequency of electrons in the material.
WRITE THIS ON THE SAME PAPER AS TODAY'S WARM-UP ACTIVITY.

10. Opaque materials
In opaque materials, any coordinated vibrations given by light to the atoms and molecules are turned into random kinetic energy - that is, into internal energy and become warmer.
Opaque materials absorb light without re- emission.

11. Shadows
Shadows usually have a dark part (or total shadow called an "umbra") on the inside and a lighter part around the edges (a partial shadow called a "penumbra").
Penumbras appear where some of the light is blocked but where other light fills in.

12. Parts of shadows

13. Reminders:
Turn in today's assignment: Be sure you name, date, and class period are on your paper with the Warm-Up activity and today's notes.
Lab tomorrow!
Be sure to turn in yesterday's assignment if you haven't already (see the white board).