Two syllables ≈ 0.2 s delay (0.1 s per syllable); distance = v·t/2 = 330·0.2/2 = 33 m, so option B.
1012
A tuning fork whose frequency as given by manufacturer is 512 Hz is being tested with an accurate oscillator. It is found that the fork produces a beat of 2 Hz when oscillator reads 514 Hz but produces a beat of 6 Hz when oscillator reads 510 Hz. The actual frequency of fork is
For the same length, the fundamental of an open-open pipe is f = v/2L while for a closed-open pipe it is f = v/4L, so the open pipe's fundamental is double the closed pipe's.
1014
The speed of bodies exceeding the speed of sound is called
‘Sweetness’ (purity of tone) is related to the periodicity and regularity of the waveform rather than amplitude or wavelength.
1016
The disc of a siren having 60 holes makes 420 revolutions per minute. What is the frequency of sound produced? (velocity of sound given but not needed)
420 rpm = 7 rps; with 60 holes per revolution frequency = 60 × 7 = 420 Hz (option b and c numerically match, b is the standard form).
1017
Assertion (A): The velocity of sound in air increases due to presence of moisture in it. Reason (R): The presence of moisture in air lowers the density of air. Of these statements:
Moist air has lower average molecular mass (and effectively lower density for same pressure), increasing sound speed; the reason correctly explains the assertion.
1018
Two trains A and B approach a stationary observer from opposite sides with speeds 15 m/s and 30 m/s respectively. Observer hears no beats. If frequency of whistle of train B is 504 Hz, the frequency of whistle of A is (Speed of sound = 330 m/s)
No beats implies observed frequencies equal: f_A*(v/(v -15)) = 504*(v/(v -30)); solving f_A = 504*(315/300) ≈ 529 Hz.
1019
An organ pipe closed at one end has fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a normal person can hear is:
A pipe closed at one end produces odd harmonics (3f,5f,...); with f=1500 Hz audible up to ~20 kHz, there are six overtones (odd harmonics beyond the fundamental) ≤ 20 kHz.
