Tag: theories on light

Questions Related to theories on light

On a hot summer night,the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally , the Huygen's principle leads us to conclude that as it travel,the light beam:

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

  1. bends downwards

  2. bends upwards

  3. becomes narrower

  4. goes horizontally without any deflection

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Correct Option: C

Huygens' principle is used to

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

  1. obtain the new position of wavefront geometrically

  2. explain principle of superposition of waves

  3. explain interference

  4. explain polarization

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Correct Option: C

When light suffers reflection at the interface between water and glass, the change of phase in the reflected wave is

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

  1. Zero

  2. $\pi$

  3. $\pi$/2

  4. 2$\pi$

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Correct Option: B
Explanation:

On reflection from denser medium, phase reversal occurs i.e. phase change $=\pi$ takes place, because glass is much denser than water.

On reflection from a plane surface, the following two characteristics get changed :

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

  1. Wavelength

  2. Frequency

  3. Velocity

  4. Amplitude

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Correct Option: C,D
Explanation:

On reflection from a plane surface velocity and amplitude of the incident ray changes whereas wavelength and frequency does not change.

Huygen's originally thought that for the propagation of light waves wavefront is required.

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

  1. True

  2. False

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Correct Option: A
Explanation:

The above statement is true.

As Huygens' principle lets you predict where a given wavefront will be in the future, if you have the knowledge of where the given wavefront is in the present.

The wave theory of Light was proposed by ...............

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

  1. Newton

  2. Huygens

  3. Frenel

  4. Yung

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Correct Option: B
Explanation:

Newton has given the theory that light is made of tiny particles. In 1678, Dutch physicist, Christiaan Huygens, believed that light was made up of waves vibrating up and down perpendicular to the direction of light, and therefore formulated a way of visualizing wave propagation. This known as 'Huygens' Principle'. 

Who proposed wave nature of light ?

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

  1. Huygen

  2. Young

  3. Fresnel

  4. Maxwell

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Correct Option: A
Explanation:

Huygens believed that light was made up of waves vibrating up and down perpendicular to the direction of  the light travels. This is known as 'Huygens' Principle'.  According to this theory, light waves are spherical, and these wave surfaces advance or spread out as they travel at the speed of light. This theory explains why light shining through a pin hole or slit will spread out rather than going in a straight line.

The shape of the nodal curves is 

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

  1. Elliptical

  2. Parabolic

  3. Hyperbolic

  4. Circular

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Correct Option: C

Mark the CORRECT statements(s)

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

  1. Direction of wave propagation is along the normal to wavefront.

  2. For a point source of light, the shape of wavefront can be considered to be plane at very large

    distance from the source.

  3. A point source of light is placed at the focus of a thin spherical lens, then the shape of the wavefront for emerged light may be plane.

  4. The shape of the wavefront for the light incident on a thin spherical lens (kept in vacuum) is plane, the shape of the wavefront corresponding to emergent light would be always spherical.

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Correct Option: A,B,C,D
Explanation:

According to convention, direction of wave propagation is along the normal to wavefront.

The wavefront of a point source of light is spherical. A sphere with large radius is like a plane at its surface. Thus for a point source of light, the shape of wavefront can be considered to be plane at very large distance from the source.
Beam of light from a point source emerges parallel to principle axis when kept at focus of a thin spherical lens. Thus the wavefront emergent from the lens is planar.

A: The corpuscular theory fails in explaining the velocities of light in air and water.
B: According to corpuscular theory, the light should travel faster in a 'denser medium than in a rarer medium.

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

  1. If both A and B are true but the B is the correct explanation of A

  2. If both A and B are true but the B is not the correct explanation of A

  3. If A is true but B is false

  4. If both the A and B are false

  5. If B is true but A is false

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Correct Option: A
Explanation:

Corpuscular theory fails to explain the velocity of light in air and water because it predicted light to have more velocity in denser medium where as the fact is just the opposite. So option (a) is correct.