Chapter 8 Concept Quiz
1. Which of the following is a true wave?
a. A row of falling dominoes
b. Ripples on the surface of a pond, extending outward from a pebble dropped
in the water
c. A large water wave coming into the beach, one that surfers can ride on
d. Water rushing downstream
(a) and (c)
2. Which wave has the larger or “higher” frequency, and which carries more energy?
a.
b.
c.
d.
The top wave has higher frequency and carries more energy
The top wave has higher frequency but the bottom wave carries more energy
The bottom wave has higher frequency and carries more energy
The bottom wave has higher frequency but the top wave carries more energy
(c)
3. Suppose that the two waves (below) were of equal amplitude and that the wave on
the left was a 2 cm crest (high point), and the wave on the right was a 2 cm trough (low
point). The resulting interference would be:
a.
b.
c.
d.
e.
4 cm crest
2 cm crest
Flat
4 cm trough
2 cm trough
(c)
What if both waves were 2 cm troughs? (d)
4. Give an example of (a) a one-dimensional medium, (b) a two-dimensional medium, (c)
a three-dimensional medium.
(a) Undisturbed Rope, (b) Surface of a lake, (c) Space in a room
5. Describe the experimental evidence supporting that claim that light is a wave.
In Young’s double-slit experiment, a single light source was sent through two
very small and narrow parallel slits, which acted as two light sources with synchronized
vibrations. Young demonstrated the wave nature of light by the interference pattern that
was produced on the viewing screen.
6. How do we know that the medium for light waves is not air?
We know that light does not use air as its medium for travel because we receive
light from the sun and there is no air in space between Earth and the sun.
7. Give two reasons that the force between bar magnets cannot be the electric force.
(1) bar magnets do not interact with charged objects and (2) bar magnets always
have a pair of poles, both north and south; whereas, charged objects are either only
positively or negatively charged. Not both types of charge on each end.
8. What is meant by an electric current?
An electric current is a flow of charged particles.
9. Name and briefly describe the three kinds of subatomic particles found in atoms.
The three subatomic particles found in atoms are the proton, neutron, and
electron. The proton has a positive charge and is located in the nucleus of the atom.
Neutrons have no charge and are also in the nucleus. Electrons are negatively charged
and orbit the nucleus.
10. Which force fields would be felt by a stationary charged object: gravitational, electric,
or magnetic? By a moving uncharged object? By a moving charged object?
All three objects would feel an imperceptible gravitational force due to their mass.
Both the stationary and moving charged objects would feel an electric force due to their
charge. Only the moving charge would feel a magnetic force due to the magnetic
properties of moving charges
11. What does Faraday’s law say about magnets and wires? What does it say about
magnetic fields and electric fields?
Faraday’s law says that when either a magnet or loop of wire is in motion with
respect to the other object, a current is induced in the loop of wire. Stated in terms of
fields: A changing magnetic field creates an electric field.
12. Find the wavelength of an AM radio wave whose frequency is 1000 kHz (1 kHz =
1000 Hz).
13. Two small electrically charged objects are placed a certain distance apart, where
they exert an electric force of 4 N on each other. Suppose the charge on object #1 is
halved. What happens to the force? What if the charge on both objects is halved?
If q1 is halved the force is also halved. If both charges are halved the force is
reduced to 1/4th its original value.
14. You note that waves roll past your stationary boat at a rate of one wave every 3
seconds, and you estimate the distance between waves to be 15 meters. What is the
frequency of these waves?