CBSE
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 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
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
A 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
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
A longitudinal wave is represented by . The maximum particle velocity will be four times the wave velocity if
The equation of a progressive wave is where x is in metre and t is in second. The velocity of the wave is
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
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 ?