Waves and Sound - CBSE STD 12 Science JEE physics Questions

Q 1Assertion & Reason1 Mark

Assertion : The reverberation time dependent on the the shape of enclosure, position of source and observer.
Reason : The unit of absorption coefficient in $m k s$ system is metric sabine.

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Q 2Assertion & Reason1 Mark

Assertion : When a beetle moves along the sand with in a few tens of centimeters of a sand scorpion the scorpion immediately turn towards the beetle and dashes to it
Reason : When a beetle disturbs the sand, it sends pulses along the sands surface one set of pulses is longitudinal while other set is transverse.

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Q 3Assertion & Reason1 Mark

Assertion : The flash of lightening is seen before the sound of thunder is heard.
Reason $\quad$ Speed of sound is greater than speed of light

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Q 4Assertion & Reason1 Mark

Assertion : Speed of wave $=\frac{\text { Wave length }}{\text { Time period }}$
Reason : Wavelength is the distance between two nearest particles in phase.

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Q 5Assertion & Reason1 Mark

Assertion : Sound travel faster in solids than gases.
Reason : Solid possess greater density than gases.

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Q 6MCQ1 Mark

A string vibrates according to the equation $y=5 \sin \left(\frac{2 \pi x}{3}\right) \cos 20\ \pi t$, where $x$ and $y$ are in $\mathrm{cm}$ and $t$ in sec. The distance between two adjacent nodes is

A
$3 \mathrm{~cm}$
B
$4.5 \mathrm{~cm}$
C
$6 \mathrm{~cm}$
✓
$1.5 \mathrm{~cm}$

Answer: D.

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Q 7MCQ1 Mark

The equation of a travelling wave is given by $y=0.5 \sin (20 x-400 t)$ where $x$ and $y$ are in meter and $t$ is in second. The velocity of the wave is

A
$10 \mathrm{~m} / \mathrm{s}$
✓
$20 \mathrm{~m} / \mathrm{s}$
C
$200 \mathrm{~m} / \mathrm{s}$
D
$400 \mathrm{~m} / \mathrm{s}$

Answer: B.

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Q 8MCQ1 Mark

A police car horn emits a sound at a frequency $240 \mathrm{~Hz}$ when the car is at rest. If the speed of the sound is $330 \mathrm{~m} / \mathrm{s}_{\llcorner}$the frequency heard by an observer who is approaching the car at a speed of $11 \mathrm{~m} / \mathrm{s}$, is :

✓
$248 \mathrm{~Hz}$
B
$244 \mathrm{~Hz}$
C
$240 \mathrm{~Hz}$
D
$230 \mathrm{~Hz}$

Answer: A.

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Q 9MCQ1 Mark

Two waves represented by the following equations are travelling in the same medium $y_1=5 \sin 2 \pi(75 t-0.25 x)$, $y_2=10 \sin 2 \pi(150 t-0.50 x)$ The intensity ratio $I_1 / I_2$ of the two waves is

A
$1: 2$
✓
$1: 4$
C
$1: 8$
D
$1: 16$

Answer: B.

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Q 10MCQ1 Mark

A source of sound of frequency $256 \mathrm{~Hz}$ is moving rapidly towards a wall with a velocity of $5 \mathrm{~m} / \mathrm{s}$. The speed of sound is $330 \mathrm{~m} / \mathrm{s}$. If the observer is between the wall and the source, then beats per second heard will be

✓
$7.8 \mathrm{~Hz}$
B
$7.7 \mathrm{~Hz}$
C
$3.9 \mathrm{~Hz}$
D
Zero

Answer: A.

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Waves and Sound questions

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Waves and Sound JEE physics - Waves and Sound

Waves and Sound question types

Waves and Sound questions

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