Apparent Frequency

1. 35 m/s
2. 30 m/s
3. 40 m/s
4. 45 m/s

Two cars are approaching each other at an equal speed of $7.2\mathrm{km}/\mathrm{hr}$. When they see each other, both blow horns having frequency of$676\mathrm{Hz}$. The beat frequency heard by each driver will be ________ Hz. [Velocity of sound in air is $340\mathrm{m}/\mathrm{s}$.]

What is the unit of measurement of noise or sound level?

1. 6
2. 3
3. 0
4. 12

With what velocity should an observer approach a stationary sound source, so that the apparent frequency of sound should appear double the actual frequency? (v is the velocity of sound)

1. $\frac{v}{2}$

2. $3v$

3. 2V

4. V

A person can hear sound waves in the frequency range $20Hz$ to $20kHz$. Find the minimum and the maximum wavelengths of sound that is audible to the person. The speed of sound is $360m{s}^{-1}$

1. $\text{f *}=\left(\frac{\text{v}-{\text{v}}_{\text{L}}}{\text{v}+{\text{v}}_{\text{S}}}\right)\text{f}$
2. $\text{f *}=\left(\frac{\text{v}+{\text{v}}_{\text{L}}}{\text{v}-{\text{v}}_{\text{S}}}\right)\text{f}$
3. $\text{f *}=\left(\frac{\text{v}+{\text{v}}_{\text{L}}}{\text{v}+{\text{v}}_{\text{S}}}\right)\text{f}$
4. $\text{f *}=\left(\frac{\text{v}-{\text{v}}_{\text{L}}}{\text{v}-{\text{v}}_{\text{S}}}\right)\text{f}$

If a wave completes ………..in one second, its frequency is 1 Hz.

1. 90

1. <
2. >
3. = 2 x
4. = 0.5 x

1. the pitch of the source decreases
2. the velocity of sound in air increases
3. wave length of the wave becomes small
4. wavelength of the wave remains unchanged but observer receives less number of waves

1. 100 m/s
2. 175 m/s
3. 700 m/s
4. 350 m/s

A sound wave travels at a speed of 339 m/s. Its wavelength is 1.5 cm. what is the frequency of the wave? Will it be audible?

1. $256m$
2. $20.7m$
3. $332m$
4. $256\times 16m$

1. $(\frac{c+v}{c-v})$
2. $\sqrt{2}(\frac{c+v}{c-v})$
3. $\frac{(c+v)}{c\sqrt{2}}$
4. $\sqrt{2}$

1. $+2.78\%$
2. $+3.24\%$
3. $-3.24\%$
4. $-2.78\%$

1. $97Hz$
2. $100Hz$
3. $103Hz$
4. $106Hz$

1. $9m$
2. $25m$
3. $15m$
4. $\sqrt{353}m$

1. $5\%$
2. $10\%$
3. $3\%$
4. $8\%$

Two sounds having the same speed in a medium are having wavelengths $1.3m$ and $3.9m$. A person listens to these sounds. What difference would the listener feel?

1. First sound is heard with higher pitch

2. First sound is louder

3. First sound is heard with better quality

4. Second sound is heard with higher pitch

1. $0.8f,0.8\lambda$
2. $1.2f,\lambda$
3. $1.2f,1.2\lambda$
4. $0.8f,1.2\lambda$

1. 850 Hz
2. 1000 Hz
3. 750 Hz
4. 950 Hz

1. 4 $\times$ 10${}^6$ Hz
2. 3.2 $\times$ 10${}^7$ Hz
3. 5 $\times$ 10${}^7$ Hz
4. 3 $\times$ 10${}^6$ Hz

1. The listener is moving towards the source of sound
2. The listener and source of sound are moving with same velocity
3. The listener and the source of sound are stationary
4. None of the above

1. 0.008286