Waves Test

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Waves Test - 7

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Weekly Quiz Competition

Question 1
1 / -0

Two sinusoidal waves on the same string exhibit interference, adding or cancelling according to the principle of superposition. If the two are travelling in the same direction and have the same amplitude a and frequency but differ in phase by a phase constant φ, the result is a single wave with the same frequency ω :If φ = 0 or an integral multiple of 2 π, . The waves are exactly

A
in phase and the interference is destructive.

B
out of phase and the interference is constructive.

C
in phase and the interference is constructive.

D
out of phase and the interference is desstructive.

Solution

As two waves are in same phase (vibration is in same direction) so their amplitudes are added together & hence interference will be constructive. The condition that arise from superposition principle for constructive interference is

∅ = 2nπ
Question 2
1 / -0

A travelling wave, at a rigid boundary or a closed end,

A
is reflected with a phase difference of 30^o

B
is reflected with a phase reversal

C
is reflected with a phase difference of 70^o

D
is reflected with same phase

Solution

In reflection of this kind there must be node at the support as the string is fixed there. The reflected and incident pulses must have opposite signs, so as to cancel each other at that point. Thus in case of a travelling wave, the reflection at rigid boundary will take place with a phase reversal or with a phase difference of 180⁰
Question 3
1 / -0

Standing waves are characterized by fixed locations of zero displacement called nodes and fixed locations of maximum displacements called antinodes. The separation between two consecutive nodes or antinodes is.

A
λ/2

B
λ/4

C
λ

D
3λ /2

Solution

At locations x = 0,λ/2, λ, 3λ/2, ... called the nodes the amplitude is always zero, whereas at locations x = λ/4, 3λ/4, 5λ/4, ... called the anti-nodes, the amplitude is maximum. The distance between two consecutive nodes or anti-nodes is λ/2.
Question 4
1 / -0

A string of length L fixed at both ends or an air column closed at one end and open at the other end, vibrates with frequencies called its normal modes. Each of these frequencies is

A
a sub harmonic frequency of the system

B
an excitation frequency of the system

C
a forced frequency of the system

D
a resonant frequency of the system

Solution

A resonant frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object. ... It is easy to get an object to vibrate at its resonant frequencies, hard to get it to vibrate at other frequencies.A string of length L fixed at both ends or an air column closed at one end and open at the other end, vibrates with frequencies called its normal modes. Each of these frequencies is called resonant frequency of the system.
Question 5
1 / -0

Beats arise when two waves having slightly different frequencies, ν₁ and ν₂ and comparable amplitudes, are superposed. The beat frequency is

A
ν_beat = 2ν₁∼ ν₂

B
ν_beat = ν₁ − ν₂

C
ν_beat = ν₁ + ν₂

D
ν_beat = ν₁ ∼ 2ν₂

Solution

The beat frequency is always equal to the difference in frequency of the two notes that interfere to produce the beats. So if two sound waves with frequencies of 256 Hz and 254 Hz are played simultaneously, a beat frequency of 2 Hz will be detected.
Question 6
1 / -0

The human ear is most sensitive to sound in the frequency range of

A
200 to 400 Hz

B
10000 to 20000 Hz

C
20 to 20000 Hz

D
1000 to 2000 Hz

Solution

Humans are most sensitive to (i.e. able to discern at lowest intensity) frequencies between 2,000 and 5,000 Hz. The human ear can respond to minute pressure variations in the air if they are in the audible frequency range, roughly 20 Hz - 20 kHz. ... This incredible sensitivity is enhanced by an effective amplification of the sound signal by the outer and middle ear structures.
Question 7
1 / -0

in transverse waves, the constituents of the medium

A
oscillate at 40^∘ to the direction of wave propagation

B
oscillate at 30^∘ to the direction of wave propagation

C
oscillate perpendicular to the direction of wave propagation

D
oscillate parallel to the direction of wave propagation

Solution

In transverse wave motion medium particles oscillates or vibrates in a direction perpendicular to the direction of wave propagation to form crest & trough in the wave motion.
Question 8
1 / -0

in longitudinal waves, the constituents of the medium

A
oscillate along the direction of wave propagation.

B
oscillate at 30^∘ to the direction of wave propagation

C
oscillate perpendicular to the direction of wave propagation

D
oscillate at 40^∘ to the direction of wave propagation

Solution

In longitudinal wave motion, medium particles oscillates or vibrates in same direction of wave propagation to produce compression & rarefaction in wave propagation.
Question 9
1 / -0

Travelling or progressive wave

A
does not move from one point of the medium to all others

B
does not move from one point of the medium to another

C
does not move from one point of the medium to any other

D
travels from one point of the medium to another

Solution

As progressive wave means a wave propagating in some onward direction in the medium

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Waves Test - 7

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Waves Test - 7

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Question 1

in phase and the interference is destructive.

out of phase and the interference is constructive.

in phase and the interference is constructive.

out of phase and the interference is desstructive.

Solution

Question 2

is reflected with a phase difference of 30o

is reflected with a phase reversal

is reflected with a phase difference of 70o

is reflected with same phase

Solution

Question 3

λ/2

λ/4

λ

3λ /2

Solution

Question 4

a sub harmonic frequency of the system

an excitation frequency of the system

a forced frequency of the system

a resonant frequency of the system

Solution

Question 5

νbeat = 2ν1 ∼ ν2

νbeat = ν1 − ν2

νbeat = ν1 + ν2

νbeat = ν1 ∼ 2ν2

Solution

Question 6

200 to 400 Hz

10000 to 20000 Hz

20 to 20000 Hz

1000 to 2000 Hz

Solution

Question 7

oscillate at 40∘ to the direction of wave propagation

oscillate at 30∘ to the direction of wave propagation

oscillate perpendicular to the direction of wave propagation

oscillate parallel to the direction of wave propagation

Solution

Question 8

oscillate along the direction of wave propagation.

oscillate at 30∘ to the direction of wave propagation

oscillate perpendicular to the direction of wave propagation

oscillate at 40∘ to the direction of wave propagation

Solution

Question 9

does not move from one point of the medium to all others

does not move from one point of the medium to another

does not move from one point of the medium to any other

travels from one point of the medium to another

Solution

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is reflected with a phase difference of 30^o

is reflected with a phase difference of 70^o

ν_beat = 2ν₁∼ ν₂

ν_beat = ν₁ − ν₂

ν_beat = ν₁ + ν₂

ν_beat = ν₁ ∼ 2ν₂

oscillate at 40^∘ to the direction of wave propagation

oscillate at 30^∘ to the direction of wave propagation

oscillate at 30^∘ to the direction of wave propagation

oscillate at 40^∘ to the direction of wave propagation