Using Huygens'S Construction of Secondary Wavelets Explain How a Diffraction Pattern is Obtained on a Screen - Physics


Using Huygens's construction of secondary wavelets explain how a diffraction pattern is obtained on a screen due to a narrow slit on which a monochromatic beam of light is incident normally.



Consider a parallel beam of light from a lens falling on a slit AB. As diffraction occurs, the pattern is focused on the screen with the help of lens L2. We will obtain a diffraction pattern that is a central maximum at the centre O, flanked by a number of dark and bright fringes called secondary maxima and minima.

Each point on the plane wave front AB sends out secondary wavelets in all directions. The waves from points equidistant from the centre C, lying on the upper and lower half, reach point O with zero path difference and, hence, reinforce each other producing maximum intensity at point O.

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2014-2015 (March) Delhi Set 2


On the basis of Huygens' wave theory of light prove that velocity of light in a rarer medium is greater than velocity of light in a denser medium.

Explain the construction of plane wavefront using Huygens’ principle.

What is the shape of the wavefront in the following case:

The portion of the wavefront of light from a distant star was intercepted by the Earth.

State Huygen's principle.

Consider a plane wave front incident on a thin convex lens. Draw a proper diagram to show how the incident wave front traverses through the lens and after refraction focusses on the focal point of the lens, giving the shape of the emergent wave front.

Use Huygens' principle to verify the laws of refraction.

The refractive indices of water and diamond are `4/3` and 2.42 respectively. Find the speed of light in water and diamond. (c = 3x108 m/s)

Using this principle draw a diagram to show how a plane wave front incident at the interface of the two media gets refracted when it propagates from a rarer to a denser medium. Hence verify Snell's law of refraction.

State Huygens’s principle. Show, with the help of a suitable diagram, how this principle is used to obtain the diffraction pattern by a single slit.

Draw a plot of intensity distribution and explain clearly why the secondary maxima becomes weaker with increasing order (n) of the secondary maxima.

Huygens' principle of secondary wavelets may be used to

(a) find the velocity of light in vacuum

(b) explain the particle behaviour of light

(c) find the new position of a wavefront

(d) explain Snell's Law

Light waves travel in vacuum along the X-axis. Which of the following may represent the wave fronts?

Derive the law of reflection using Huygen’s Wave Theory. 

With what type of source of light are cylindrical wave fronts associated?

Answer the following question.
Define the term wavefront. Using Huygen's wave theory, verify the law of reflection.

Define a wavefront. Using 'Huygens' principle, draw the shape of a refracted wavefront, when a plane wave is incident on a convex lens.

Define the term 'wavefront of light'. A plane wavefront AB propagating from a denser medium (1) into a rarer medium (2) is incident of the surface P1P2 separating the two media as shown in fig.
Using Huygen's principle, draw the secondary wavelets and obtain the refracted wavefront in the diagram.

According to Huygen's construction, relation between old and new wavefront is ______.

What is the geometrical shape of the wavefront for:

  1. Light diverging from a point source?
  2. The pattern of wavefront of the light from a distant star intercepted by earth?

What is the phase difference between any two points lying on the same?

The inverse square law of intensity is valid for a

Wavefront means

Huygen's conception of secondary waves ______.

What is the shape of the wavefront on earth for sunlight?

Two light beams of intensities in the ratio of 9 : 4 are allowed to interfere. The ratio of the intensity of maxima and minima ______.

What type of wavefronts are associated with a source infinity?

Using Huygen's wave theory of light, show that the angle of incidence is equal to the angle of reflection. Draw a neat and labelled diagram.


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