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Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

If light waves emitted by an ordinary source, for what period of time, the phase remains constant :-

  1. $10 sec$
  2. $1 sec$
  3. $10^{-3}$ sec
  4. $10^{-8}$ sec
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In ordinary light sources, light is emitted due to independent atomic transitions lasting roughly 10^-8 seconds, during which the phase remains relatively constant before a sudden random phase change occurs.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Huygen's theory of secondary waves can be used of find-

  1. Velocity of light

  2. The wavelength of light

  3. Wave front geometrically

  4. Magnifying power of microscope
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Huygens principle states that every point on a wavefront acts as a source of secondary spherical wavelets, allowing us to geometrically construct the position of a wavefront at any subsequent time.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Coherent sources can be obtained:

  1. only by division of wave front

  2. only by division of amplitude

  3. both by division of amplitude and wave front

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Coherent sources can be created by dividing the wavefront (e.g., Young's double slit) or by dividing the amplitude (e.g., thin film interference).

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Assertion  $(A):$  Microwaves are better carries of signals than optical waves
Reason  $(R):$  Microwaves move faster than optical waves

  1. Both $A$ and $R$ are true and $R$ is correct explanation of $A$
  2. Both $A$ and $R$ are true and $R$ is not the correct explanation of $A$
  3. $A$ is true but $R$ is false
  4. $A$ is false but $R$ is true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
A frequency of an optical wave is more than the microwave so optical waves are better canes of the signal, therefore, A is false. In medium (other than vacuum) speed of 0 microwaves 1A greater than optical wave hence R 1A true.
Ans. (D)