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Questions Related to physics

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.

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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

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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

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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. 

Ray optics is valid when characteristic dimensions are

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

  1. of the same order as the wavelength of light

  2. much smaller than the wavelength of light

  3. much larger than the wavelength of light

  4. of the order of 1 mm

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Correct Option: C
Explanation:

Ray optics is valid when characteristics dimensions are larger than the wavelength of the light, so that rectilinear property of light can be used.

Who first proposed that light was wave-like in character ?

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

  1. Huygens

  2. Newton

  3. Young

  4. Maxwell

Show answer
Correct Option: A
Explanation:

Huygens 

In 1678, Dutch physcist, christian Huygens beived that light was made up of waves vibrating up and down perpendicular to the direction of the light travels, and therefore formulated a way of visualising wave propagation. This became known as Huygens Principe. 

A : The phase difference between any two points on a wave front is zero
R : From the source light, reaches every point on the wave front in the same time.

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

  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 correct explanation of A

  3. A is true but R is false

  4. A is false but R is true

Show answer
Correct Option: A
Explanation:

A wave front is the locus of points having the same phase.
Thus statement A is true because the phase difference is zero as all points have same phase.
Statement R is true because a wavefront is composed of all points where the light reaches from the source in the same time.
As light takes the same time it has the same phase at all points on a wavefront and hence it correctly explains statement A.

1: Primary waves can travel in all directions in an ether
2: Secondary waves can travel only in backward in an ether

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

  1. 1 is true, 2 is false

  2. Both 1 and 2 are true

  3. 1 is false, 2 is true

  4. Both 1 and 2 are false

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Correct Option: A
Explanation:

Primary wave can travel in all directions in ether.
Secondary waves can travel in forward direction in ether

According to Huygens, the ether medium pervading entire universe is

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

  1. Less elastic and more dense

  2. Highly elastic and less dense

  3. Not elastic

  4. Much heavier

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Correct Option: B
Explanation:

Huygen considered, light needs a medium to propagate  called ether which is highly elastic and less denser.

The wave theory of light, in its original form, was first postulated by.

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

  1. Isaac Newton

  2. Christian Huygens

  3. Thomas Young

  4. Augustin Jean Fresnel

Show answer
Correct Option: B
Explanation:

B

In 1678, Dutch physicist, Christian Huygens,  believed that the light was made up of waves vibrating up and down perpendicular to the direction of the light travels and therefore formulated away of visualising wave propagation. This becomes know as Huygens principle. Huygens theory was the successful theory of light in three dimensions. Huygens suggested that the light wave peaks form from surfaces like the layers of onion. In a vacuum or other uniform mediums the light waves are spherical and these wave surfaces advance or spread out as they travel at the speed if light. This theory explains why light shining through a pinhole or slitwall spread out rather than going in straight lines.