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

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:

  1. bends downwards

  2. bends upwards

  3. becomes narrower

  4. goes horizontally without any deflection
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since the refractive index increases with height, the upper part of the light beam travels slower than the lower part near the ground. According to Huygens' principle, this differential speed causes the wavefronts to tilt such that the beam bends upward.

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. Newton

  2. Huygens

  3. Frenel

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

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

Who proposed wave nature of light ?

  1. Huygen

  2. Young

  3. Fresnel

  4. Maxwell
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Mark the CORRECT statements(s)

  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.
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
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.

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

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.

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