Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is

1. negative and
2. positive.

In the given figure the radius of curvature of the curved face in the planoconvex and the planoconcave lens is 15 cm each. The refractive index of the material of the lenses is 1.5. Find the final position of the image formed.

(i) In Young's double-slit experiment, deduce the condition for (a) constructive and (b) destructive interferences at a point on the screen. Draw a graph showing variation of intensity in the interference pattern against position 'x' on the screen.

(b) Compare the interference pattern observed in Young's double-slit experiment with single-slit diffraction pattern, pointing out three distinguishing features.

Derive an expression for path difference in Young’s double slit experiment and obtain the conditions for constructive and destructive interference at a point on the screen.

In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?

Draw the intensity pattern for single slit diffraction.

Draw the intensity pattern for double slit interference.

State differences between interference and diffraction patterns.

Use Huygens' principle to verify the laws of refraction.

Write three characteristic features to distinguish between the interference fringes in Young's double slit experiment and the diffraction pattern obtained due to a narrow single slit.

In Young's double slit experiment, derive the condition for

(i) constructive interference and

(ii) destructive interference at a point on the screen.

A beam of light consisting of two wavelengths, 800 nm and 600 nm is used to obtain the interference fringes in a Young's double slit experiment on a screen placed 1 · 4 m away. If the two slits are separated by 0·28 mm, calculate the least distance from the central bright maximum where the bright fringes of the two wavelengths coincide.

How does an unpolarized light incident on a polaroid get polarized? Describe briefly, with the help of a necessary diagram, the polarization of light by reflection from a transparent medium.

Two polaroids ‘A’ and ‘B’ are kept in crossed position. How should a third polaroid ‘C’ be placed between them so that the intensity of polarized light transmitted by polaroid B reduces to 1/8^th of the intensity of unpolarized light incident on A?

 What is the effect on the interference fringes to a Young’s double slit experiment when

(i) the separation between the two slits is decreased?

(ii) the width of a source slit is increased?

(iii) the monochromatic source is replaced by a source of white light?

Justify your answer in each case.

The intensity at the central maxima in Young’s double slit experimental set-up is I₀. Show that the intensity at a point where the path difference is λ/3 is I₀/4.

Write the conditions on path difference under which constructive interference occurs in Young’s double-slit experiment.

In a single slit diffraction experiment, the width of the slit is increased. How will the

1. size and
2. intensity

of central bright band be affected? Justify your answer.

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 fig.

Using Huygen’s principle, draw the secondary wavelets and obtain the refracted wave front in the diagram.

In Young's double slit experiment using light of wavelength 600 nm, the slit separation is 0.8 mm and the screen is kept 1.6 m from the plane of the slits. Calculate

1. the fringe width
2. the distance of (a) third minimum and (b) fifth maximum, from the central maximum.