CBSE
Multiple Choice QuestionsA car moving with a velocity of 36 km/h crosses a siren of frequency 500 Hz. The apparent frequency of siren after passing it will be
520 Hz
485 Hz
540 Hz
460 Hz
A hollow cylinder with both sides open generates a frequency f in air. When the cylinder vertically immersed into water by half its length the frequency will be
f
2f
f/2
f/4
The equation of a progressive wave is where x is in metre and t is in second. The velocity of the wave is
Two stretched strings have lengths land 2l while tension are T and 4 T respectively. If they are made of same material the ratio of their frequency is
2 : 1
1 : 2
1 : 1
1 : 4
The frequency of the first overtone of a closed pipe of length l1 is equal to that of the first overtone of an open pipe of length l2. The ratio of their lengths (l1 : l2) is
2 : 3
4 : 5
3 : 5
3 : 4
A train approaching a railway platform with a speed of 20 ms-1 starts blowing the whistle. Speed of sound in air is 340 ms-1. If the frequency of the emitted sound from the whistle is 640 Hz, the frequency of sound to a person standing on the platform will appear to be
600 Hz
640 Hz
680 Hz
720 Hz
Two tuning forks of frequency n1 and n2 produces n beats per second. If n1 and n2 are known, n1 may be given by
n2n
n2 ± n
A plane progressive wave is given by y = 2 cos 6.284 (330t − x). What is the period of the wave ?
When sound is produced in an aeroplane moving with a velocity of 200 m/s horizontal its echo is heard after 10 s. If velocity of sound in air is 300 ms-1 the elevation of aircraft is
250 m
1250 m
2500 m
A longitudinal wave is represented by . The maximum particle velocity will be four times the wave velocity if
