Questions · Page 3 of 3

1 Marks Question

Question 1011 Mark
Can two astronauts talk on the surface of moon as they do on earth?
Answer
No, the astronauts cannot talk on the surface of moon as there is no atmosphere (air) on moon. Sound waves cannot travel without a medium.
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Question 1021 Mark
For the harmonic travelling wave $\text{y}=2\cos2\pi(10\text{t}-0.0080\text{x}+3.5)$ where x and y are in cm and t is second. What is the phase difference between the oscillatory motion at two points separated by a distance of:

0.5m

Answer
$\text{y}=2\cos2\pi(10\text{t}-0.0080\text{x+3.5})$
$\text{y}=2\cos(20\pi\text{t}-0.0016\pi\text{x}+7.0\pi)$
Wave is propagated in $+\text{x}$ direction because $\omega\text{t}$ and kx are in with opposite sign standard equation $\text{y}=\text{a}\cos(\omega\text{t}-\text{kx}+\phi)$
a = 2, $\omega=20\pi,\ \text{k}=0.016\pi$ and $\phi=7\pi$
Path differencee p = 0.5m = 50cm
$\Delta\phi=\text{kp}=0.016\pi\times50=0.8\pi$ red.
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Question 1031 Mark
What change is observed when a wave gets reflected from a hard, rigid support?
Answer
A phase change of $\pi$ radians.
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Question 1041 Mark
What is the nature of ultrasonic waves and what is their frequency?
Answer
Ultrasonic waves are longitudinal waves in nature and have frequency greater than 20kHz.
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Question 1051 Mark
Given below are some functions of x and t to represent the displacement of an elastic wave.
$\text{y}=4\sin(5\text{x}-\text{t/ 2})+3\cos(5\text{x}-\text{t/ 2})$
Answer
A stationary wave of the for $\text{y}=5\cos(4\text{x})\sin20\text{t}$ is a stationary wave so (b) (i).
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Question 1061 Mark
What is the relation between velocity of the wave (v) frequency of the wave (v) and wavelength of the wave $(\lambda)$?
Answer
$\text{v}=\text{v}\lambda$
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Question 1071 Mark
Why is sound heard in water more intense in comparison to sound heard in air?
Answer
This is because intensity of sound increases with increase in density of the medium.
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Question 1081 Mark
Where does the pressure of larger magnitude exist at nodes or at antinodes?
Answer
Pressure is maximum at points of minimum displacement. So, it is maximum at nodes.
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Question 1091 Mark
Name the factors affecting the velocity of sound in a medium.
Answer
Temperature, density and ratio $\gamma$ affect the velocity of sound in a medium.
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Question 1101 Mark
Give one similarity and one difference between a S.H.M. and a Wave.
Answer
Similarity- Periodic nature.
Difference- Wave is a function of position and time, while a SHM is a function of time only.
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Question 1111 Mark
What type of graph you expect between speed of sound through a gas and pressure of gas?
Answer
The graph will be straight line parallel to pressure axis.
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Question 1121 Mark
Is it possible to have longitudinal waves on a string a transverse wave in a steel rod?
Answer
No, because string is not stretchable. It can neither be compressed nor rarefied. Yes, transverse waves are possible in steel rod, because steel has elasticity of shape.
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Question 1131 Mark
What is the difference between a tone and a note?
Answer
Note is sound of particular frequency, while tone is of a particular intensity.
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1 Marks Question - Page 3 - Physics STD 11 Science Questions - Vidyadip