Tag: theories on light

Questions Related to theories on light

Choose the Correct answer from alternative given.
The idea of secondary wavelets for the propagation of a wave was first given by:

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

  1. Newton

  2. Huygens

  3. Maxwell

  4. Fresnel

Show answer
Correct Option: B
Explanation:

According to the Huygens theory, all the points on a  wavefront act as source for a secondary wavefront or a wavelet which spread outward from the point and move at the speed of light.

The phenomena which is not explained by Huygen's construction of the wavefront

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

  1. reflection

  2. diffraction

  3. refraction

  4. origin of spectra

Show answer
Correct Option: D
Explanation:

The Huygen's construction of wavefront does not explain the phenomena of origin of spectra.

Wavefront is the locus of all points, where the particles of the medium vibrate with the same.

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

  1. phase

  2. amplitude

  3. frequency

  4. period

Show answer
Correct Option: A
Explanation:

Wavefront is the locus of all points, where the particles of the medium vibrate with the same phase

The wavelength of characteristic $X \text { -ray } K _ { \alpha }$ a line emitted by hydrogen like atom is $0.32 \mathrm { A } ^{ \circ }$. The wavelength of $K _ { \beta }$ line emitted by the same element is 

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

  1. $0.21 { \mathrm { A } }$

  2. $0.27 \mathrm { A }$

  3. $0.33 \mathrm { A }$

  4. $0.40 \hat { \mathrm { A } }$

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Correct Option: A

A transverse wave travelling in a denser medium is reflected from a rarer medium. Then, 

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

  1. an incident crest is reflected as a crest

  2. an incident crest is reflected as a trough

  3. there is a phase change of $2\pi$ rad

  4. there is a phase change of $\pi/2$ rad

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Correct Option: A

The radius of a wavefront as the waves propagate

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

  1. decreases

  2. increases

  3. becomes zero

  4. sometimes decreases and sometimes increases.

Show answer
Correct Option: B
Explanation:

As the waves propagates, it goes on creating secondary sources of light, resulting in increase in its radius.

Huygens principle of secondary waves

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

  1. allow us to find the focal length of a thick convex lens.

  2. give us the magnifying power of the microscope.

  3. is a geometrical method to find, the position of a wave front.

  4. is used to determine the velocity of light.

Show answer
Correct Option: C
Explanation:

Huygens's Principle states that every point on a wavefront is a source of secondary wavelets, which spread forward at the same speed.

Thus is enables to find the position of wavefront.

The wave front due to a source situated at infinity is :

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

  1. spherical

  2. cylindrical

  3. planar

  4. none of these

Show answer
Correct Option: C
Explanation:
  • when you considered it a large distance and measuring justice Mall section of it then it can be considered to be plane wavefront source at Infinity 
  • example the one coming from sun to earth surface is considered to be plain VU friend from light diverging from a point source will be spherical
  • So, the wave front due to a source situated at infinity is planar
  • Option  C is the right answer

Which of the following phenomena can be used to analyse a beam of light into its component wavelength?

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

  1. Reflection

  2. Refraction

  3. Polarisation

  4. Interference

Show answer
Correct Option: B
Explanation:
  • Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves  also experience refraction. 
  • How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.
  • Hence refraction is used to analyse a beam of light into its component wavelength
  • Option B is the right answer

Huygen's concept of wavelets is useful in

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

  1. explaining polarisation

  2. determining focal length of lenses

  3. determining chromatic aberration

  4. geometrical reconstruction of a wavefront

Show answer
Correct Option: D
Explanation:
Huygens considered that light was propagated in longitudinal waves.
Huygen's concept explained the direction of propagation of light waves by geometrical reconstruction of wavefront.