This Week’s Stuff: EM Waves
1. Today – No Lecture – We will solve some problems in EM Waves
2. Tuesday – (Tomorrow) – 10:00AM-12:00PM 2 – hour problem
review on Chapters 22 and 23
3. Wednesday – Holiday – No Class
4. Friday – EXAMINATION #3
a. 4-5 questions
b. Some multiple choice questions – many on Chapter 23
c. 3-4 Problems, split between the chapters; mostly impossible!
5. Monday – Begin Chapter 24/25 on Mirrors and Lenses
1
•An electromagnetic wave of wavelength 435 nm is traveling in vacuum in the  z
direction. The electric field has amplitude 2.70 103 V/m and is parallel to the x
axis. What are (a) the frequency and (b) the magnetic-field amplitude of this
wave? (From: E=cB)
2
A laser beam shines along the surface of a block of transparent material. (See the
figure .) Half of the beam goes straight to a detector, while the other half travels
through the block and then hits the detector. The time delay between the arrival of
the two light beams at the detector is 6.25 . What is the index of refraction of this
material?
3
The electric field of a sinusoidal electromagnetic wave obeys the equation
E = - (375 (V/m))sin ((5.97 * 10^15(rad/s)) t + (1.99 * 10^7(rad/m))x).
What is the amplitude of the electric field of this wave?
What is the amplitude of the magnetic field of this wave?
What is the frequency of the wave?
What is the wavelength of the wave?
What is the period of the wave?
What is the speed of the wave?
4
Medical x rays are taken with electromagnetic waves having a wavelength around
0.105 .
What is the frequency of such waves?
What is the period of such waves?
What is the wave number of such waves?
5
At a distance of 55.0
8.60×10−2
from a radio station antenna the electric-field amplitude is
.
What is the magnetic-field amplitude at this same point?
Assuming that the antenna radiates equally in all directions (which is probably not
the case), what is the total power output of the station?
At what distance from the antenna is the electric-field amplitude equal to half the
value given?
6
He-Ne lasers are often used in physics demonstrations. They produce light of wavelength
633
and a power of 0.500
these quantities can vary).
spread over a cylindrical beam 1.20
What is the intensity of this laser beam?
What is the maximum value of the electric field?
What is the maximum value of the magnetic field?
7
in diameter (although
Two plane mirrors intersect at right angles. A laser beam strikes the first of them at
a point 11.5
from their point of intersection, as shown in the figure .
For what angle of incidence at the first mirror will this ray strike the midpoint of
the second mirror (which is 28.0
long) after reflecting from the first mirror?
8
Three plane mirrors intersect at right angles. A beam of laser light strikes the first
of them at an angle with respect to the normal.
Show that when this ray is reflected off of the other two mirrors and crosses the
original ray, the angle between these two rays will be
9
.
Prove that a ray of light reflected from a plane mirror rotates through an angle
when the mirror rotates through an angle about an axis perpendicular to the
plane of incidence.
10
Light with a frequency of 5.90×1014
of refraction of 1.52.
travels in a block of glass that has an index
What is the wavelength of the light in vacuum ?
What is the wavelength of the light in the glass?
11
A glass plate having parallel faces and a refractive index of 1.55 lies at the bottom
of a liquid of refractive index 1.64. A ray of light in the liquid strikes the top of the
glass at an angle of incidence of 60.0 degrees.
Compute the angle of refraction of this light in the glass.
12
A beam of light in air makes an angle of 52.0 with the surface (not the normal) of
a glass plate having a refractive index of 1.76.
What is the angle between the reflected part of the beam and the surface of the
glass?
What is the angle between the refracted beam and the surface (not the normal) of
the glass?
13
A beam of light in air makes an angle of 52.0 with the surface (not the normal) of
a glass plate having a refractive index of 1.76.
What is the angle between the reflected part of the beam and the surface of the
glass?
What is the angle between the refracted beam and the surface (not the normal) of
the glass?
14
A parallel-sided plate of glass having a refractive index of 1.55 is in contact with
the surface of water in a tank. A ray coming from above makes an angle of
incidence of 29.6 with the top surface of the glass.
What angle does this ray make with the normal in the water?
15
As shown in the figure , a layer of water covers a slab of material
ray of light traveling upwards follows the path indicated.
in a beaker. A
Using the information on the figure, find the index of refraction of material
Find the angle the light makes with the normal in the air.
16
.
A ray of light in diamond (index of refraction 2.42) is incident on an interface with
air.
What is the largest angle the incident ray can make with the normal in diamond
and not be totally reflected back into the diamond?
17
At the very end of Wagner's series of operas The Ring of the Nibelung, Brünnhilde
takes the golden ring from the finger of the dead Siegfried and throws it into the
Rhine, where it sinks to the bottom of the river.
Assuming that the ring is small enough to be treated as a point compared with the
depth of the river and that the Rhine is 10.0 deep where the ring goes in, what is
the area of the largest circle at the surface of the water over which light from the
ring could escape from the water?
18
Light is incident along the normal to face AB of a glass prism of refractive index
1.52, as shown in the figure .
Find the largest value the angle can have without any light refracted out of the
prism at face AC if the prism is immersed in air.
Find the largest value the angle can have without any light refracted out of the
prism at face AC if the prism is immersed in water.
19
The polarizing angle for light in air incident on a glass plate is 56.6 degrees.
What is the index of refraction of the glass?
20