Tag: physics

Questions Related to physics

Which surfaces are said to be smooth?

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. As long as the irregularities of surfaces are small as compared to the wavelength of the incident light.

  2. As long as surface irregularities are large compared to the wavelength of the incident light.

  3. As long as surface smoothness are small as compared to wavelength of reflected light

  4. As long as the surface irregularities are large as compared to the wavelength of reflected light.

Show answer
Correct Option: A
Explanation:

A surface behaves as a smooth surface as long as the surface irregularities are small compared with the wavelength of the incident light.

Light reflecting from surface of sea rocks is an example of:

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. Regular reflection

  2. Diffused reflection

  3. Total internal reflection

  4. None of these

Show answer
Correct Option: B
Explanation:

When a light ray is reflected in many directions from a surface like a rock, it is called as diffused (or Irregular) reflection.

The change in reflected wave, when light wave suffers reflection at the interface from air to glass is?

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. $0$

  2. $\dfrac{\pi}{2}$

  3. $\pi$

  4. $2\pi$

Show answer
Correct Option: C
Explanation:
When light wave suffers reflection at the interface from air to glass, the change in phase of the reflected wave is equal to π
Hence the option C is the right answer

The reflection taking place from the walls of a building is called:

physics reflection of light and shadow regular and irregular reflection regular and diffused reflection laws of reflection

  1. regular reflection

  2. diffused reflection

  3. multiple reflection

  4. internal reflection

Show answer
Correct Option: B
Explanation:

The reflection taking place from the walls of a building is called diffused reflection.
In diffused reflection, the reflected rays are not parallel to each other. This kind of reflection occurs from a coarse surface. Walls of a building being coarse surfaces, give rise to diffused reflections.

The wave used by artificial satellites for communication is

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. Microwaves

  2. Infrared rays

  3. Radio rays

  4. X-rays

Show answer
Correct Option: A
Explanation:

Microwaves are mostly used for satellite communication, as microwaves can pass straight through the atmosphere and connect antennas on earth to satellite in earth's orbit.

The critical velocity of satellite of mass $100 kg$ moving round a planet is $20 m/s$. If another satellite of mass $200 kg$ is kept moving in the same orbit then its critical velocity will be:

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. $40 km/hr$

  2. $72 km/hr$

  3. $40 m/s$

  4. $72 m/s$

Show answer
Correct Option: B

In sky wave communication which of the frequency will be reflected back by the ionospheric layer having electron density $4 \times 10 ^ { 6 } / \mathrm { m } ^ { 3 }$

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. $19 \times 10 ^ { 3 } \mathrm { Hz }$

  2. $9 \times 10 ^ { 3 } H z$

  3. $31 \times 10 ^ { 3 } \mathrm { Hz }$

  4. $20 \times 10 ^ { 3 } \mathrm { Hz }$

Show answer
Correct Option: B

The examples of broadcast are
A) radio B) television
C) telephony D) internet

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. A & B

  2. A, B & D

  3. A,B & C

  4. B & D

Show answer
Correct Option: B
Explanation:

telephone is one to one, whereas internet can have have many ways of communication, but radio and television broadcast the messages.

A digital signal

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. is less reliable than analog signal

  2. is more reliable than analog signal

  3. is equally reliable as the analog signal

  4. Not at all reliable

Show answer
Correct Option: B
Explanation:

Noise is added to digital signal also but its easier to remove the noise and amplify the digital signals as compared to analog signals, because analog signals contain many frequencies.

Statement A: If the antenna is vertical,a vertically polarised EM wave is radiated
Statement B: The vertically polarised EM wave has electrical variations in the vertical plane

physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

  1. A is true but B is false

  2. A is false but B is true

  3. A and B are false

  4. A and B are true

Show answer
Correct Option: D
Explanation:

Polarization of wave depends upon the orientation of the antenna. direction of polarization is along the orientation of antenna. By convention, direction of polarization of an EM wave is along the variation of electric field.