Tag: theories on light

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

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

  1. Newton

  2. Huygens

  3. Maxwell

  4. Fresnel
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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 

  1. $0.21 { \mathrm { A } }$
  2. $0.27 \mathrm { A }$
  3. $0.33 \mathrm { A }$
  4. $0.40 \hat { \mathrm { A } }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Moseley's law and hydrogen-like atomic energy levels, the frequency of characteristic X-rays is proportional to (Z - b)^2 and inversely proportional to squared wavelength differences. Using the transition formula for K-alpha and K-beta lines, the ratio of their wavelengths can be calculated, resulting in approximately 0.27 angstroms for K-beta.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a wave reflects from a rarer medium, there is no phase change. Therefore, the crest remains a crest and the trough remains a trough.

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

Huygens principle of secondary waves

  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.
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. spherical

  2. cylindrical

  3. planar

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
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
Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

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

  1. Reflection

  2. Refraction

  3. Polarisation

  4. Interference
Reveal answer Fill a bubble to check yourself
B Correct answer
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
Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Huygen's concept of wavelets is useful in

  1. explaining polarisation

  2. determining focal length of lenses

  3. determining chromatic aberration

  4. geometrical reconstruction of a wavefront
Reveal answer Fill a bubble to check yourself
D Correct answer
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.