Tag: theories on light

Questions Related to theories on light

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

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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

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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. 

Which experiment seemed to make it clear that light propogates as a wave?

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

  1. Milikan's oil drop experiment

  2. The Michelson-Morley experiment

  3. Young's double-slit experiment

  4. Fresnel's lens experiment

  5. Lenz's proof of Lenz's law

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Correct Option: C
Explanation:
Young's double slit experiment 
The double slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles. Moreover it displays the fundamentally probabislistic nature of quantum mechanical phenomena

Wave front formed by the collimator of a spectrometer

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

  1. Plane

  2. Spherical

  3. Cylindrical

  4. Paraboloidal

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Correct Option: B
Explanation:

Wave front formed by the collimator of a spectrometer is a plane wave front, when r lit is in the focus.

Indentify the correct statement from the following

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

  1. Wave nature of light was proposed by Huygen.

  2. The direction of light ray and its wave front are opposite.

  3. Huygen's wave theory could not explain phenomenon of reflection.

  4. A monochromatic ray of light after passing through the prism should be made of one colour only.

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Correct Option: A,D
Explanation:

Huygen's wave theory: This wave theory was given by Huygens in 1678. According to this theory, a source of light propagates spherical waves in hypothetical.

In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.
Huygen’s wave theory could easily explain reflection, energy transmission, and refraction, but had difficulty explaining the straight line travel of light.
When a ray of monochromatic light would pass through a prism, you would see it refract but it will not disperse as its a beam of single wavelength. When light enters a medium with a different density it bends (refracts). Because white light contains a collection of component colors with varying wavelengths.

Huygen's concept of secondary wave

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

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

  2. is a geometrical method to find a wavefront

  3. is used to determine the velocity of light

  4. is used to explain polarization

Show answer
Correct Option: B
Explanation:

Huygen proposed a hypothesis for the geometrical construction of the position of a common wavefront at any instant during the propagations of waves in a medium.