Waves

To raise the pitch of a certain piano string, the piano tuner: 

A. loosens the string 

B. tightens the string 

C. shortens the string 

D. lengthens the string 

E. removes some mass

Two identical strings, A and B, have nearly the same tension. When they both vibrate in their fundamental resonant modes, there is a beat frequency of 3 Hz. When string B is tightened slightly, to increase the tension, the beat frequency becomes 6 Hz. This means: 

A. that before tightening A had a higher frequency than B, but after tightening, B has a higher frequency than A 

B. that before tightening B had a higher frequency than A, but after tightening, A has a higher frequency than B 

C. that before and after tightening A has a higher frequency than B 

D. that before and after tightening B has a higher frequency than A 

E. none of the above

“Beats” in sound refer to: 

A. interference of two waves of the same frequency 

B. combination of two waves of slightly different frequency 

C. reversal of phase of reflected wave relative to incident wave 

D. two media having slightly different sound velocities 

E. effect of relative motion of source and observer

A complete cycle of wave is around 

A. 90° 

B. 180° 

C. 45° 

D. 360°

For a given medium, the frequency of a wave is: 

A. independent of wavelength 

B. proportional to wavelength 

C. inversely proportional to wavelength 

D. proportional to the amplitude 

E. inversely proportional to the amplitude 

Two pipes are each open at one end and closed at the other. Pipe A has length L and pipe B has length 2L. Which harmonic of pipe B matches in frequency the fundamental of pipe A? 

A. The fundamental 

B. The second 

C. The third 

D. The fourth 

E. There are none

To produce beats it is necessary to use two waves: 

A. traveling in opposite directions 

B. of slightly different frequencies 

C. of equal wavelengths 

D. of equal amplitudes 

E. whose ratio of frequencies is an integer

Unification of electromagnetic and weak nuclear forces was done by

A. Maxwell

B. Faraday

C. Kirchhoff

D. Abdus-Salam

When a 100-Hz oscillator is used to generate a sinusoidal wave on a certain string the wavelength is 10 cm. When the tension in the string is doubled the generator produces a wave with a frequency and wavelength of: 

A. 200 Hz and 20 cm 

B. 141 Hz and 10 cm 

C. 100 Hz and 20 cm 

D. 100 Hz and 14 cm 

E. 50 Hz and 14 cm

If the length of a piano wire (of given density) is increased by 5%, what approximate change in tension is necessary to keep its fundamental frequency unchanged? 

A. Decrease of 10% 

B. Decrease of 5% 

C. Increase of 5% 

D. Increase of 10% 

E. Increase of 20%