Physics 11th Chap 9 : Topic 14 - Maryam Publications

Physics Chapter 9 : Topic 14

Beats

1 / 30

Beats are produced when two waves have:

A) Different wavelengths and no interference

B) Slightly different frequencies and interfere with each other

C) Different amplitudes but same frequency

D) Same frequency and same amplitude

2 / 30

The periodic variation in loudness caused by interference of two waves is called:

A) Diffraction

B) Resonance

C) Beats

D) Polarization

3 / 30

The beat frequency produced by two waves of frequencies $\mathbf{f}_{\mathbf{1}}$ and $\mathbf{f}_{\mathbf{2}}$ is:

A) $\mathbf{f}_{\mathbf{1}}\mathbf{\times}\mathbf{f}_{\mathbf{2}}$

B) $\mathbf{f}_{\mathbf{1}}\mathbf{+}\mathbf{f}_{\mathbf{2}}$

C) $\left| \mathbf{f}_{\mathbf{1}}\mathbf{-}\mathbf{f}_{\mathbf{2}} \right|$

D) $\mathbf{f}_{\mathbf{1}}\mathbf{\ /\ }\mathbf{f}_{\mathbf{2}}$

4 / 30

Two tuning forks produce frequencies $\mathbf{256\ Hz}$ and $\mathbf{260\ Hz}$. The beat frequency will be:

A) $\mathbf{16\ Hz}$

B) $\mathbf{0.98\ Hz}$

C) $\mathbf{4\ Hz}$

D) $\mathbf{516\ Hz}$

5 / 30

During beats, the loud sound occurs when the two waves:

A) Have different speeds

B) Interfere constructively

C) Completely cancel each other

D) Have zero amplitude

6 / 30

The soft sound in a beat phenomenon occurs due to:

A) Reflection

B) Destructive interference

C) Refraction

D) Constructive interference

7 / 30

Two sound waves have frequencies $\mathbf{500\ Hz}$ and $\mathbf{504\ Hz}$. The number of beats heard per second is:

A) $\mathbf{4}$

B) $\mathbf{500}$

C) $\mathbf{2}$

D) $\mathbf{1004}$

8 / 30

If two sound waves have exactly the same frequency, the beat frequency will be:

A) Equal to frequency of sound

B) Maximum

C) Double the frequency

D) Zero

9 / 30

The phenomenon of beats demonstrates:

A) Wave reflection only

B) Wave polarization only

C) Wave interference

D) Wave absorption

10 / 30

For audible beats to be clearly detected, the difference between frequencies should generally be:

A) Very large

B) Very small

C) Equal to the speed of sound

D) Zero only

11 / 30

Two waves of frequencies $\mathbf{400\ Hz}$ and $\mathbf{410\ Hz}$ produce:

A) $\mathbf{810}$ beats per second

B) No beats

C) $\mathbf{5}$ beats per second

D) $\mathbf{10}$ beats per second

12 / 30

In the beat phenomenon, the frequency of individual waves remains:

A) Zero

B) Continuously decreasing

C) Continuously increasing

D) Constant

13 / 30

The sound intensity in beats varies because:

A) The resultant amplitude changes periodically.

B) The medium stops vibrating.

C) The wavelength becomes zero.

D) The frequency changes continuously.

14 / 30

Two waves produce maximum loudness when their phase difference is:

A) $\mathbf{0}$ or $\mathbf{2\pi}$

B) $\mathbf{\pi}$

C) Random

D) $\mathbf{\pi\ /\ 2}$

15 / 30

Two waves produce minimum loudness when their phase difference is:

A) $\mathbf{\pi}$

B) $\mathbf{2\pi}$

C) $\mathbf{4\pi}$

D) $\mathbf{0}$

16 / 30

If the frequency difference between two waves increases, the beat frequency:

A) Remains unchanged

B) Decreases

C) Increases

D) Becomes zero

17 / 30

A musician uses beats to tune an instrument because:

A) Beats eliminate sound

B) Beats measure amplitude

C) Beats indicate the difference between frequencies

D) Beats increase sound frequency

18 / 30

A tuning fork of unknown frequency produces $\mathbf{5}$ beats per second with a $\mathbf{300\ Hz}$ tuning fork. Its frequency may be:

A) $\mathbf{305\ Hz}$ only

B) $\mathbf{295\ Hz}$ only

C) $\mathbf{295\ Hz}$ or $\mathbf{305\ Hz}$

D) $\mathbf{300\ Hz}$ exactly

19 / 30

If two waves have frequencies $\mathbf{100\ Hz}$ and $\mathbf{102\ Hz}$, the time interval between successive beats is:

A) $\mathbf{2\ s}$

B) $\mathbf{1\ s}$

C) $\mathbf{0.5\ s}$

D) $\mathbf{102\ s}$

20 / 30

Beats are not usually produced by two independent light sources because:

A) Light sources are generally incoherent.

B) Light cannot interfere.

C) Light has no frequency.

D) Light has no wavelength.

21 / 30

The mathematical expression for resultant amplitude of two interfering waves depends on:

A) Their phase difference

B) Their colour only

C) Their speed only

D) Their medium only

22 / 30

When two waves of slightly different frequencies interfere, the resultant wave has:

A) Constant amplitude

B) No frequency

C) Periodically changing amplitude

D) Zero amplitude

23 / 30

Two sound waves have frequencies $\mathbf{700\ Hz}$ and $\mathbf{710\ Hz}$. The beat period is:

A) $\mathbf{0.1\ s}$

B) $\mathbf{710\ s}$

C) $\mathbf{0.01\ s}$

D) $\mathbf{10\ s}$

24 / 30

In beat formation, the resultant frequency of sound heard is approximately:

A) Twice the frequency difference

B) Zero

C) The difference of frequencies

D) The average frequency of the two waves

25 / 30

If two tuning forks produce 8 beats per second, their frequencies differ by:

A) $\mathbf{0\ Hz}$

B) $\mathbf{4\ Hz}$

C) $\mathbf{8\ Hz}$

D) $\mathbf{16\ Hz}$

26 / 30

Which condition is necessary for producing audible beats?

A) Frequencies must be extremely different.

B) Amplitudes must be zero.

C) Frequencies must be slightly different.

D) Frequencies must be exactly equal.

27 / 30

At maximum intensity during beats, the resultant amplitude is:

A) Maximum

B) Zero

C) Minimum

D) Constant

28 / 30

At minimum intensity during beats, the resultant amplitude is:

A) Infinite

B) Minimum

C) Doubled

D) Maximum

29 / 30

If two sound sources have frequencies differing by $\mathbf{20\ Hz\ }$, the number of beats heard per second is:

A) $\mathbf{40}$

B) $\mathbf{10}$

C) $\mathbf{20}$

D) $\mathbf{0}$

30 / 30

The beat phenomenon is an application of:

A) Photoelectric effect

B) Principle of superposition

C) Conservation of momentum

D) Coulomb’s law

Your score is

0%