Assertion:  The fundamental frequency of an open organ pipe increases as the temperature is increased. 

Reason:  This is because as the temperature increases, the velocity of sound increases more rapidly than length of the pipe.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Two waves represented by y = a sin( ωt - kx )  and  y = a cos( ωt- kx ) are superposed. The resultant wave will have an amplitude

• a

• $\sqrt{2} \mathrm{a}$

• 2 a

• zero

Assertion: To hear distinct beats, difference in frequencies of two sources should be less than 10. 

Reason: More the number of beats per sec
more difficult to hear them.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Astronomical wavelength increase due to doppler effect known as

• Red shift

• Voilet shift

• UV

• IR shift

What is your observation when two sources are emitting sound with frequency 499 Hz and 501 Hz?

• Frequency of 500 Hz is heard with change in intensity take place twice.

• Frequency of 500 Hz is heard with change in intensity take place once.

• Frequency of 2 Hz is heard with change in intensity take place once.

• Frequency of 2 Hz is heard with change in intensity take place twice.

A uniform string is vibrating with a fundamental frequency  ' f ' . The new frequency, if radius & length both are doubled would be

•  2f

• 3f

• $\frac{\mathrm{f}}{4}$

• $\frac{\mathrm{f}}{3}$

The second overtone of an open pipe has the same frequency as the first overtone of a closed pipe 2 m long. The length of the open pipe is

• 8 m

• 4 m

• 2 m

• 1 m

Let T₁ and T₂ be the time periods of springs A and B when mass M is suspended from one ·end of each spring. If both springs are taken in series and the same mass M is suspended from the series combination, the time period is T then

• T₁ + T₂ +T₃

• $\frac{1}{\mathrm{T}} = \frac{1}{{\mathrm{T}}_1} + \frac{1}{{\mathrm{T}}_2}$

• T² = ${\mathrm{T}}_1^{ 2} + {\mathrm{T}}_2^{ 2}$

• $\frac{1}{{\mathrm{T}}^2} = \frac{1}{{\mathrm{T}}_1^{ 2}} + \frac{1}{{\mathrm{T}}^2}$

Two closed organ pipes of length 100 cm and 101 cm produces 16 beats in 20 sec. When each pipe is sounded in its fundamental mode. Calculate the velocity of sound.

• 303 ms^-1

• 332 ms^-1

• 323.2 ms^-1

• 300 ms^-1yes

A siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s. The frequency of sound heard by listener is ( velocity of sound = 300 m/s )

• 727.3 Hz

• 481.2 Hz

• 644.8 Hz

• 286.5 Hz