Wave optics

Previous Years' CBSE Board Questions

10.3 Refraction and Reflection of Plane Waves using Huygens Principle

MCQ

1. According to Huygens principle, the amplitude of secondary wavelets is
2. egual in both the forward and the backward directions.
3. maximum in the forward direction and zero in the backward direction.
4. large in the forward direction and small in the backward direction.
5. small in the forward direction and large in the backward direction. (2023) R

2 A plane wavefront is incident on a concave mirror of radius of curvature R. The radius of the refractive wavefront will be

1. 2R (b) R (c) <math>\frac{R}{2}</math> (d) 4

(2023) 😈

A plane wavefront is incident on a surface

separating two media of refractive indices <math>n_1</math> and

<math>n_2</math> (> <math>n_1</math>). With the help of a suitable diagram, explain

its propagation from the rarer to denser medium.

Hence, verify Snell's law. (2022C) An

A plane wavefront is propagating from a rarer into a

denser medium. Use Huygens principle to show the

refracted wavefront and verify Snell's law.

(Term II 2021-22)

1. Define the term, "refractive index" of a medium, Verify Snell's law of refraction when a plane wavefront is propagating from a denser to a rarer medium. (Delhi 2019) (Ap)
2. Define the term wavefront. Using Huygens wave theory, verify the law of reflection. (Delhi 2019)

Define the term wavefront. State Huygen's principle.

Consider a plane wavefront incident on a thin

convex lens. Draw a proper diagram to show how the

incident wavefront traverses through the lens and

after refraction focusses on the focal point of the

lens, giving the shape of the emergent wavefront.

(2 marks) SAI

(Al 2016)

1. Define wavefront of a travelling wave. Using Huygens principle, obtain the law of refraction at a plane interface when light passes from a rarer to a denser medium. (2020)
2. Define the term 'wavefront of light'. A plane wave front AB propagating from denser medium (1) into a rarer medium (2) is incident on the surface P₁P₂ separating the two media as shown in figure.

Using Huygens' principle, draw the secondary wavelets and obtain the refracted wavefront in the diagram. (2020) An (1) <math>P_2</math> (2)

SA II (3 marks)

1. A plane wave-front propagating in a medium of refractive index 'µ1' is incident on a plane surface making an angle of incidence (i). It enters into a medium of refractive index <math>\mu_2</math> (<math>\mu_2 > \mu_1</math>). Use Huygen's construction of secondary wavelets to trace the refracted wavefront. Hence, verify Snell's law of refraction. (2023) Ev

Using Huygen's construction, show how a plane wave is reflected from a surface. Hence verify the law of reflection. (2023)

LA (5 marks)

in a liquid of reference index <math>\mu</math>, the new fringe width

will be

1. β (b) (c)

1. What is a wavefront? How does it propagate? Using Huygens' principle, explain reflection of a plane wavefront from a surface and verify the laws of reflection. (2/5, 2020)

OR Define a wavefront. Using Huygen's principle verify the laws of reflection at a plane surface.

(2018) Ap

Define wavefront. Use Huygen's principle to verify the laws of refraction. (3/5, Al 2017)

1. Define a wavefront. How is it different from a ray?
2. Depict the shape of a wavefront in each of the following cases.
3. Light diverging from point source.
4. Light emerging out of a convex lens when a point source is placed at its focus.
5. Explain the following, giving reasons:
6. When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency.
7. When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a reduction in the energy carried by the wave? (2/3 Al 2016) [An
8. Use Huygens principle to show how a plane wavefront propagates from a denser to rarer medium. Hence verify Snell's law of refraction.

(AI 2015) III

A plane wavefront propagating in a medium of

refractive index '\(\mu_1'\) is incident on a plane surface

making the angle of incidence i as shown in the figure.

It enters into a medium of refraction of refractive

index '<math>\mu_2</math>' (<math>\mu_2 > \mu_1</math>). Use Huygens' construction of

secondary wavelets to trace the propagation of the

refracted wavefront. Hence verify Snell's law of

refraction. (Foreign 2015)

<math>\mu\beta</math>

VSA (1 mark)

1. Young's double slit experiment is performed by using green, red and blue monochromatic light sources, one at a time. The value of the fringe width will be maximum in case of _____ light. (2020C) R
2. In Young's double slit experiment, the path difference between two interfering waves at a point on the screen is <math>\frac{5\lambda}{2}</math>, <math>\lambda</math> being wavelength of the light used. The ____ dark fringe will lie at this point. (2020)

If one of the slits in Young's double slit experiment

is fully closed, the new pattern has ____ central

maximum in angular size. (2020) (Ap)