1. A six slit stroboscope wheel is used to stop an image of a water wave. The stroboscope takes
25 s to turn 20 times. While looking through the strobe, it can be easily seen that the
wavelength of the wave is 12 cm.
a) Determine the wave frequency by assuming the strobe is at the highest "stopping
frequency.
b) Calculate the speed of the wave.
2. A wave stopped by a stroboscope causes a trough to pass a point every 0.10 s. The distance
between the first and seventh crest is 14.4 cm.
a) Calculate the wavelength?
b) Determine the speed of the wave?
3. A source of a wave has a frequency of 8.0 Hz.
a) State the frequency of the wave produced by the source?
b) With a four slits stroboscope, explain what you would see if the strobe frequency was
1, 2, and 4 revolutions per second.
c) The magnification factor of the observing screen used to observe the wave is 2.5 to 1.
The distance between the first and seventh crest for the wave is 28.5 cm.
1) Calculate the wavelength.
2) What is the velocity of the wave?
4. Circular waves in a ripple tank have successive wave fronts that differ in radius by 4.0 cm. If
the speed of the wave is 40 cm/s, what is the frequency of the source?
5. A water wave with speed 40 cm/s travels into shallow water where the speed is 30 cm/s. The
angle of incidence is 30o and the frequency of the source is 10 Hz. Calculate
a) the relative index of refraction.
b) the wavelengths in in the deep and shallow water.
c) the angle of refraction.
6. A sound wave moves from cold air to warm air with an angle of incidence of 30o. The velocity
of the sound wave in the incident medium is 320 m/s, and 384 m/s in the refractive medium.
Determine the angle of refraction for the wave.
7. For the previous question, what is the refractive angle if the incident angle is 60o? Explain
yourself.
8. A wave enters the shallow region of a ripple tank at an angle of refraction of 45o. The angle of
incidence in the deep region of the tank is 60o. Calculate the ratios in the two region of the
a) wave-lengths?
b) velocities?
c) frequencies?
9. Wave fronts encounter the boundary between deep and shallow water at an angle of 60o. The
angle of refraction in the shallow water is 30o. If the wave in the deep water has a wavelength
of 2.0 cm, and the source of the waves has a frequency of 11 Hz, what is the speed of the
wave in the shallow and deep water?
10. In region A of a ripple tank, straight waves (plane waves) have a wavelength of 2.0 cm, and
frequency of 6.0 Hz. The boundary between regions A and B makes an angle of 30o with the
wave crests of the incident wave. In region B, the angle between wave crests and the
boundary is 20o.
a) Calculate the relative refractive index of the two regions.
b) Determine the velocity of the wave in each region.
11. Two openings in a barrier in a ripple tank act as sources for waves that produce an
interference pattern. The distances from the two openings to a point on the second nodal line
in the interference pattern are 25 cm and 29.5 cm. If the speed of the waves is 7.5 cm/s, find
the wavelength and frequency of the wave.
12. Two in phase sources produce an interference patter in a ripple tank. The two sources are
12.0 cm and 20.0 cm from a point on the second nodal line. It takes the waves 2.0 s to
travel 30 cm. Determine the velocity, wavelength, and frequency of the wave.
13. Two in phase sources 5.0 cm apart each have a frequency of 6.0 Hz. Two points on the first
nodal lines on either side of the central anti nodal line are 20 cm apart. Each of these points
are 50 cm from the midpoint of the line joining the two sources. Find the speed and
wavelength of the waves.
14. The broadcast frequency of a radio station is 1.0 X 106 Hz. The station broadcasts from two
antenna which are 400 m apart along an east west line. These two towers broadcast in phase,
and the speed of the radio waves are 3.00 X 108 m/s.
a) Determine the direction to the points 20 km north of the towers, that are on the first
anti nodal lines.
b) If the towers are in opposite phase, what are the directions to the first nodal lines north
of the towers?
November 22, 2013