Tag: physics

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Questions Related to physics

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

When a tuning fork of 500 Hz is used, the first and second resonating lengths of closed air column are found to be 18 cm and 54 cm respectively. Find the velocity of sound in S.I. system.

  1. $120{ms}^{-1}$

  2. $240{ms}^{-1}$

  3. $360{ms}^{-1}$

  4. $480{ms}^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a closed pipe, the resonance lengths are L1 = lambda/4 and L2 = 3*lambda/4. The difference L2 - L1 = lambda/2, so lambda = 2 * (54 - 18) = 72 cm = 0.72 m. Velocity v = f * lambda = 500 * 0.72 = 360 m/s.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

An observer measures speed of light to be C when he is stationary with respect to the source. If the observer moves with velocity $\displaystyle v$ towards the source then the velocity of light observed will be :

  1. $\displaystyle c- v$

  2. $\displaystyle c + v$

  3. $\displaystyle \sqrt{1-v^2/c^2}$

  4. $\displaystyle c$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Speed of light does not change with the frame of reference.  Option 'D' is correct.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The frequency of fundamental mode of vibration of an air column enclosed in a closed end pipe is 250 Hz. If its length is 33 cm, then find the velocity of sound in air.

  1. $390 {ms}^{-1}$

  2. $160 {ms}^{-1}$

  3. $330 {ms}^{-1}$

  4. $150 {ms}^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a closed pipe, the fundamental frequency f = v / (4 * L). Given f = 250 Hz and L = 33 cm = 0.33 m, v = f * 4 * L = 250 * 4 * 0.33 = 1000 * 0.33 = 330 m/s.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

A wave has a frequency of $5$ GHz.
What is the period of the wave?

  1. $200$ ps

  2. $0.2$ ns

  3. $20$ ns

  4. $20000$ $\mu s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,


Frequency $f=5 GHz=5\times10^{9}\ Hz$


The period of the wave is reciprocal of frequency.

$T=\dfrac{1}{f}$

$T=\dfrac{1}{5\times10^{9}}$

$T=2\times10^{-10}$

$T=0.2\ ns$

The period of the wave is $0.2\ ns$

Hence, B is correct option.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

Which of the following product of $e, h, \mu, G$ (where $\mu$ is the permeability) be taken so that the dimensions of the product are same as that of the speed of light?

  1. $h e^{-2} \mu^{-1} G^0$

  2. $h^2 e G^0 \mu$

  3. $h^0 e^2 G^{-1} \mu$

  4. $h G e^{-2} \mu^{0}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The speed of light c has dimensions [LT^-1]. Using the relation c = 1/sqrt(mu_0 * epsilon_0), and checking dimensions of h, e, G, mu, the combination h * e^-2 * mu^-1 yields the correct dimensions of velocity.

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

Which of the following does not has fundamental unit?

  1. Mass

  2. Time

  3. Force

  4. length
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The fundamental units are the units of the fundamental quantities, as defined by the International System of Units. They are not dependent upon any other units, and all other units are derived from them. There are seven basic fundamental quantities: Length, mass, time, electric current, amount of substance, luminous intensity & temperature. The quantities which are derived with the help of these basic physical quantities are called derived quantities. They are density, volume, pressure, force, etc.

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

The wavelength of light is usually expressed in

  1. Micron

  2. Fermi

  3. Nanometer

  4. Angstrom
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Angstrom $(\dot A)$ unit of length used chiefly in measuring wavelengths of light, equal to $10^{-10}$ metre, or $0.1$ nanometer.  It is used to express wavelengths of visible light, ultraviolet (UV) light, X rays, and gamma rays.

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

In a tug-of-war between the teams A and B, the rope breaks at a point which is nearer to A. Then

  1. A has applied more force

  2. B has applied more force

  3. A and B both have applied same force

  4. Neither has applied any force
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a tug-of-war, the tension throughout the rope is uniform. If the rope breaks, it is due to a structural weakness at that point, not because one side pulled harder than the other.