Oscillations and Waves (NEET (National Eligibility cum Medical Entrance Test) Physics): Questions 161  165 of 195
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Question number: 161
» Oscillations and Waves » Harmonics
Question
A string on a musical instrument is 70 cm long and its fundamental frequency is 235 Hz. If the desired frequency of 950 Hz, is to be produced, the required length of the string is
Choices
Choice (4)  Response  

a.  22.7 cm 

b.  12.3 cm 

c.  17.3 cm 

d.  16.5 cm 

Passage
A plate was cut from a quartz crystal and is used to control the frequency of an oscillating electrical circuit. Longitudinal standing waves are set up in the plate with displacement antinodes at opposite faces.
The fundamental frequency of vibration is given by the equation . Here s is thickness of the plate and density of quartz is 2658.76 kg/m ^{3}.
Question number: 162 (1 of 2 Based on Passage) Show Passage
» Oscillations and Waves » Harmonics
Question
If the quartz plate is vibrating in 3 ^{rd} harmonic while measuring the frequency of 1.2 ⨯ 10 ^{6} Hz, then the thickness of the plate is,
Choices
Choice (4)  Response  

a.  7.175 cm 

b.  0.07 cm 

c.  6.02 cm 

d.  71.75cm 

Question number: 163 (2 of 2 Based on Passage) Show Passage
» Oscillations and Waves » Harmonics
Question
Young’s modulus of elasticity for quartz is 
Choices
Choice (4)  Response  

a.  8.76 ⨯ 10 ^{12} N/m ^{2} 

b.  7 ⨯ 10 ^{11} N/m ^{2} 

c.  2 ⨯ 10 ^{12} N/m ^{2} 

d.  Information insufficient 

Question number: 164
» Oscillations and Waves » Beats
Question
Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the midpoint of the line joining them. Now the whistle B and the listener start moving with speed 30 m/s away from the whistle A. If speed of sound be 330 m/s, how many beats will be heard by the listener?
Choices
Choice (4)  Response  

a.  4 

b.  2 

c.  8 

d.  6 

Question number: 165
» Oscillations and Waves » Doppler Effect in Sound
Question
A whistle sends out 256 waves in a second. If the whistle approaches the observer with velocity 1/3 of the velocity of sound in air, the number of waves per second the observer will receive,
Choices
Choice (4)  Response  

a.  384 

b.  300 

c.  200 

d.  192 
