A hearing test is conducted on an aged person. It is found that her threshold of hearing is 20 dB at 1 kHz , and it rises linearly with frequency to, 60 dB at, 9 kHz . The minimum intensity of sound that the person can hear at, 5 kHz is,

0 . 05 times than that at 9 kHz

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The intensity ratio of two waves is 1:9. The ratio of their amplitudes, is

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Important Questions on Waves

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A uniform string of length $20 m$ is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the support is

(Take, $g = 10 m s^{- 2}$ )

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A hearing test is conducted on an aged person. It is found that her threshold of hearing is

20 dB

1 kHz

, and it rises linearly with frequency to,

60 dB

at,

9 kHz

. The minimum intensity of sound that the person can hear at,

5 kHz

is,

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

The intensity of sound during the festival season increased by,

100

times. This could imply a decibel level rise from-

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

The pressure wave,

P = 0.01 \sin [1000 t - 3 x] N m^{- 2}

, corresponds to the sound produced by a vibrating blade on a day when atmospheric temperature is

0 ° C

. On some other day when temperature is

T

, the speed of sound produced by the same blade and at the same frequency is found to be

336 m s^{- 1}

. Approximate value of

T

is:

EASY

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A travelling harmonic wave is represented by the equation

y (x, t) = 10^{- 3} \sin (50 t + 2 x),

where

x

and

y

are in meter and

t

is in seconds. Which of the following is a correct statement about the wave?

MEDIUM

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A small speaker delivers

2 W

of audio output. At what distance from the speaker will one detect

120 d B

intensity sound? [Given reference intensity of sound as

10^{- 12} W / m^{2}

]

HARD

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A particle performing S.H.M. starts from the equilibrium position and its time period is

16 s

. After

2 s

its velocity is

π m s^{- 1} .

Amplitude of oscillation is

(\cos 45^{o} = \frac{1}{\sqrt 2})

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

For a transvers wave travelling, along a straight line, the distance between two peaks (crests) is

5 m

, while the distance between one crest and one trough is

1.5 m

. The possible wavelengths (in

m

) of the waves are:

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A string of length

1 m

and mass

5 g

is fixed at both ends. The tension in the string is

8 .0 N

. The string is set into vibration using an external vibrator of frequency

100 Hz

. The separation between successive nodes on the string is close to

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A simple harmonic motion is represented by:

y = 5 (\sin 3 π t + \sqrt{3} \cos 3 π t) cm

The amplitude and time period of the motion are:

EASY

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

Which characteristic of sound, makes it possible to recognize a person by his voice without seeing him?

EASY

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

Two waves of amplitudes

A_{1}

and

A_{2}

respectively are superimposed. The ratio between the maximum and minimum intensities of the resultant waves is

9 : 4

. The value of

\frac{A_{2}}{A_{1}}

is [Assume

A_{1} > A_{2}

]

EASY

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A uniform thin rope of length

12 m

and mass

6 kg

hangs vertically from a rigid support and a block of mass

2 kg

is attached to its free end. A transverse short wave train of wavelength

6 cm

is produced at the lower and the rope. What is the wavelength of the wave train (in

cm

) when it reaches the top of the rope?

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A tunning fork of frequency

480 H z

is used in an experiment for measuring speed of sound

(v)

in air by resonance tube method. Resonance is observed to occur at two successive lengths of the air column,

l_{1} = 30 c m

and

l_{2} = 70 c m .

Then,

ν

is equal to:

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

When a particle of mass

m

is attached to a vertical spring of spring constant

k

and released, its motion, is described by

y (t) = y_{0} \sin^{2} ωt

, where '

y

' is measured from the lower end of upstretched spring. Then

ω

is :

EASY

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

Sound waves of wavelength

λ

and velocity

v

in medium-

1

enter medium-

2

. If their velocity in medium-

2

4 v

, the wavelength in medium-

2

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A transverse wave propagating on a stretched string of linear density $3 \times 10^{- 4} {kgm}^{- 1}$ is represented by the equation

$y = 0.2 \sin (1.5 x + 60 t)$

where, $x$ in metres and $t$ is in seconds. The tension in the string (in Newton) is

HARD

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

Two vectors

\vec{A}

and

\vec{B}

are defined as

\vec{A} = a \hat{i}

and

\vec{B} = a (\cos ω t \hat{i} + \sin ω t \hat{j})

, where a is a constant and

ω = \frac{π}{6} rad s^{- 1} .

|\vec{A} + \vec{B}| = \sqrt{3} |\vec{A} - \vec{B}|

at time

t = τ

for the first time, the value of

τ

in seconds, is_______

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Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

A uniform rope of length

L

and mass

m_{1}

, hangs vertically from a rigid support. A block of mass

m_{2}

is attached to the free end of the rope. A transverse pulse of wavelength

λ_{1}

is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is

λ_{2}

. The ratio

\frac{λ_{2}}{λ_{1}}

is:

HARD

Physics>Oscillations and Waves>Waves>Displacement Relation for a Progressive Wave

The clocktower ("ghantaghar") of Dehradun is famous for the sound of its bell, which can be heard, albeit faintly, upto the outskirts of the city

8 km

away. Let the intensity of this faint sound be

30 dB .

The clock is situated

80 m

high. The intensity at the base of the tower is:-

The intensity ratio of two waves is 1:9. The ratio of their amplitudes, is

Important Questions on Waves

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