1. How do these work?

3. When light (or sound) enters a new medium, the wave can be:
1/___________________ back into the original medium;
2/ __________________ at the boundary; or,
3/____________________into the new medium
reflected
absorbed
transmitted
reflected
ray
incident
ray
medium 1
energy absorbed
(boundary heats)
boundary
medium 2
transmitted
ray
Which wave (ray) has the most energy?
Which has the greatest amplitude?
incident
incident

4. When light passes into a denser medium,
it__________________.
slows down
c = 3.0 x 108 m/s
a/ In vacuum:
v = ___________________
molecules
b/ In water: c c c c
Light is________________, then _______________from
each molecule. _____________ molecules, it travels at a
speed______________.
absorbed
emitted
Between
v = c
c/ In glass: c c c c c c c
Higher density  _____________________
_____________________
more interactions
slower speed

5. Ex. Light passing from air into glass : ________________
vglass < vair
Ex. Light passing from air into glass : ________________
Characteristics of the incident ray:
vi  _______________________________
fi  _______________________________
li  _______________________________
Ai  _______________________________
determined by medium
color
found from l = v/f
energy in wave
incident
ray
air
(medium 1)
boundary
glass
(medium 2)

6. Characteristics of the reflected ray:vr fr lr Ar
= vi, b/c it is in the same medium
= fi, b/c it’s the same color
= li, b/c l = v/f
< Ai, b/c not all energy is reflected
incident
ray
reflected
ray
air
(medium 1)
boundary
glass
(medium 2)

7. Characteristics of the transmitted ray: v2 f2 l2 A2 < v1 (given)
= fi, b/c it’s the same color
< li, b/c l = v/f
< A1 b/c not all energy is transmitted
incident
ray
reflected
ray
air
(medium 1)
boundary
glass
(medium 2)
transmitted
ray
exactly the same
Notice: fr, fi, and f2 are ___________________________!!!

8. When you put your hand
in water…
Does it look like this…
or this?
Water

9. In the new medium, the speed _____________ and
frequency_________________________ , so the wavelength
must ________________________ .
Different materials slow the __________________ by
different amounts. How much it slows is summed up
in a quantity called the ______________________________
n, of a material. It is defined as the ratio of the speed
of light _______________________ to the speed of light
__________________________:
"n" is called the ___________________ index because
"slowing down" can cause light to ______________ (bend).
Notice that n _______________________ because it is the
______________________________________________________ .
changes
remains the same
also change
speed of light
absolute index of refraction ,
in a vacuum, c,
in the material, v
n = c/v
refractive
refract
has no units
ratio of two speeds, and the units cancel.

10. Physics Reference Tables, page 5, top:

11. Page 2, bottom:
Note:
This table
is really only
true for yellow
light, and only
approximately
true for other
frequencies

12. Ex: Determine the speed of (yellow) light in water.
Given:
nwater =
1.33
c = 3.00 x 108 m/s
Unknown:
v = ?
n = c / v
1.33 = (3.00 x 108 m/s) / v
v = x 108 m/s

13. Ex: what is the relationship between v and n?
n = c / v n
higher n  __________________
 __________________
slower speed
shorter wavelength
To compare the speeds and wavelengths of two
materials, use the equation: n2 n1 v2 v1 l2 l1 = =

14. Physics Reference Tables, page 5, top:

15. Ex: The wavelength of a certain laser in air is 780. nm. A CD is
coated with a plastic material
that has an absolute index of
refraction of Find the
wavelength of the light in the CD
laser n1
air n2 CD
Given: n2 n1 l2 v2 v1 l1 =
l1 = 780. nm
n1 = 1.00
1.55
780. nm
n2 = 1.55 =
1.00 l2
Unknown:
l2 = 780. nm/1.55
l2 = ?
l2 = 503 nm

16. Ex: Laser light entering a CD:
 shorter  can read more data