7.3. Doppler effect for sound waves
A subsection of Physics, 9702, through 7. Waves
Listing 10 of 60 questions
By reference to the direction of the propagation of energy, state what is meant by a longitudinal wave and by a transverse wave. longitudinal: transverse: The intensity of a sound wave passing through air is given by Ι = Kvρ f 2A2 where Ι is the intensity (power per unit area), K is a constant without units, v is the speed of sound, ρ is the density of air, f is the frequency of the wave and A is the amplitude of the wave. Show that both sides of the equation have the same SΙ base units. Describe the Doppler effect. A distant star is moving away from a stationary observer. State the effect of the motion on the light observed from the star. A car travels at a constant speed towards a stationary observer. The horn of the car sounds at a frequency of 510 Hz and the observer hears a frequency of 550 Hz. The speed of sound in air is 340 m s–1. Calculate the speed of the car. speed = m s–1
9702_s16_qp_22
THEORY
2016
Paper 2, Variant 2
View
Define the frequency of a sound wave. A sound wave travels through air. Describe the motion of the air particles relative to the direction of travel of the sound wave. The sound wave emitted from the horn of a stationary car is detected with a microphone and displayed on a cathode-ray oscilloscope (c.r.o.), as shown in . 1.0 cm 1.0 cm The y-axis setting is 5.0 mV cm–1. The time-base setting is 0.50 ms cm–1. Use to determine the frequency of the sound wave. frequency = Hz The horn of the car sounds continuously. Describe the changes to the trace seen on the c.r.o. as the car travels at constant speed 1. directly towards the stationary microphone, 2. directly away from the stationary microphone.
9702_s17_qp_22
THEORY
2017
Paper 2, Variant 2
View
Questions Discovered
60