Science (English Medium) कक्षा १२ - CBSE Important Questions

Explain two features to distinguish between the interference pattern in Young's double slit experiment with the diffraction pattern obtained due to a single slit.

A monochromatic light of wavelength 500 nm is incident normally on a single slit of width 0.2 mm to produce a diffraction pattern. Find the angular width of the central maximum obtained on the screen.

Estimate the number of fringes obtained in Young's double slit experiment with fringe width 0.5 mm, which can be accommodated within the region of total angular spread of the central maximum due to single slit.

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.

In Young’s double slit experiment using monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ, is K units. Find out the intensity of light at a point where path difference is λ/3.

Use Huygens’s principle to explain the formation of diffraction pattern due to a single slit illuminated by a monochromatic source of light.

When the width of the slit is made double the original width, how would this affect the size and intensity of the central diffraction band?

A slit of width 0.6 mm is illuminated by a beam of light consisting of two wavelengths 600 nm and 480 nm. The diffraction pattern is observed on a screen 1.0 m from the slit. Find:

1. The distance of the second bright fringe from the central maximum pertaining to the light of 600 nm.
2. The least distance from the central maximum at which bright fringes due to both wavelengths coincide.

A ray of light travels from a medium into the water at an angle of incidence of 18°. The refractive index of the medium is more than that of water and the critical angle for the interface between the two media is 20°. Which one of the following figures best represents the correct path of the ray of light?

For which of the following media, with respect to air, the value of critical angle is maximum?

• Assertion (A): In Young's double slit experiment all fringes are of equal width.
• Reason (R): The fringe width depends upon the wavelength of light (λ) used, the distance of the screen from the plane of slits (D) and slits separation (d).

In Young's double-slit experiment, the screen is moved away from the plane of the slits. What will be its effect on the following?

1. The angular separation of the fringes.
2. Fringe-width.

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

A proton and an α-particle have the same de-Broglie wavelength Determine the ratio of  their speeds.

Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface.

Why photoelectric effect cannot be explained on the basis of wave nature of light? Give reasons.

point out any two characteristic properties of photons on which Einstein’s photoelectric equation is based ?

Briefly explain the three observed features which can be explained by Einstein’s photoelectric equation.

State clearly how photoelectric equation is obtained using the photon pictu.re of electromagnetic radiation.

Write the three salient features observed in photoelectric effect which can be explained using this equation.

Answer the following question.
Define the term "Threshold frequency", in the context of photoelectric emission.