1. Phy2005
Applied Physics II
Spring 2017
Announcements:

2. Refraction: Snell’s Law
Last time
Refraction: Snell’s Law
All three beams (incident, reflected, and refracted) are in one plane. q1 q2
Light always travels slower in a
medium than in a vacuum, v=c/n
v: speed of light in a medium
n = c/v :index of refraction
n > 1
v1 = c/n1, v2 = c/n2
n1sinq1 = n2sinq2

3. Dispersion: index of refraction decreases with wavelength!
Air
Water

4. In glass
n (red) ≈ 1.51
n (purple) ≈ 1.53

5. q l(nm) 1  sin qred = nred sin 30o = nred/2
What is the angle between the red (4.6x1014 Hz)
and blue (6.3x1014 Hz) rays emerging from a 30o
prism as shown?
1.45
1.48
1.47
1.46
300
500
700
n, quartz
l(nm)
white
30o q
nred=1.453
nblue=1.460
lred =c/f = (3.0 x 108m/s)/(4.6x1014 Hz) = 6.5 x 10-7m = 650 nm
lblue =c/f = (3.0 x 108m/s)/(6.3x1014 Hz) = 4.8 x 10-7m = 480 nm
1  sin qred = nred sin 30o = nred/2
 qred = Arcsin (nred/2) = rad
qblue = Arcsin (nblue/2) = rad
qblue- qred = q = rad = 0.28 degrees

8. “rainbow angle” = 42 degrees

9. Reminder- last time some of you had trouble here:
There are three layers of different media as shown in the figure.
A beam of light bends as shown in the figure when it passes through
the media. What can we say about the relative index of refraction
of these materials?
The media I-II-III have indices of
refraction that get smaller
2) One of the media is a vacuum
3) One of the media is glass
4) The media I-II-III have indices of
refraction that get bigger
5) Two of the media are the same I II
III

10. nIIsinqII = nIIIsinqIII qII > qI  nI > nII
nIsinqI = nIIsinqII
nIIsinqII = nIIIsinqIII
qII > qI  nI > nII
qIII > qII  nII > nIII
nI > nII > nIII I II
III

11. Clicker Quiz Time Log in your remote! ACADEMIC HONESTY
Each student is expected to hold himself/herself to a high standard of academic honesty. Under the UF academic honesty policy. Violations of this policy will be dealt with severely. There will be no warnings or exceptions.
Log in your remote!

12. (air, diamond, ice) (diamond, ice, air) (diamond, air, ice)
Q1 As a beam goes through layers of different materials (I, II, and
III), it bends as shown in the figure. The angles in the figure
indicate the angle between each beam and the vertical line.
Those materials and their index of refraction are listed in the
table. Identify each material (material I, material II, material
III).
(air, diamond, ice)
(diamond, ice, air)
(diamond, air, ice)
(4) (air, ice, diamond)
(5) (ice, air, diamond)

13. Lenses
Converging lens
Diverging lens

14. Glass lens (nG = 1.52)
real, inverted
image

15. Same shape lenses: the higher n, the shorter f
The focal length of a lens is determined by the shape
and material of the lens.
Same shape lenses: the higher n, the shorter f
Lenses with same n: the shorter radius of curvature,
the shorter f
Typical glass, n = 1.52
Polycarbonate, n = 1.59 (high index lens)
Higher density plastic, n ≈ 1.7 (ultra-high index lens)

16. Clicker Quiz Time Log in your remote! ACADEMIC HONESTY
Each student is expected to hold himself/herself to a high standard of academic honesty. Under the UF academic honesty policy. Violations of this policy will be dealt with severely. There will be no warnings or exceptions.
Log in your remote!

17. Q2. A parallel beam of light is sent through an aquarium.
If a convex lens is held in the water, it focuses the beam (…….. ……………………. ) than outside the water
nair = 1, nwater = 1.33
closer to the lens
(b) at the same position as
(c) farther from the lens