Science (English Medium) Class 12 - CBSE Important Questions for Physics

A converging lens has a focal length of 10 cm in air. It is made of a material with a refractive index of 1.6. If it is immersed in a liquid of refractive index 1.3, find its new focal length.

Draw the sketches to differentiate between plane wavefront and spherical wavefront.

Three identical polaroid sheets P₁, P₂ and P₃ are oriented so that the pass axis of P₂ and P₃ are inclined at angles of 60° and 90° respectively with the pass axis of P₁. A monochromatic source S of unpolarised light of intensity I₀ is kept in front of the polaroid sheet P₁ as shown in the figure. Determine the intensities of light as observed by the observer at O, when polaroid P₃ is rotated with respect to P₂ at angles θ = 30° and 60°.

The intensity at the central maxima in Young’s double slit experiment is I₀. Find out the intensity at a point where the path difference is` lambda/6,lambda/4 and lambda/3.`

Write the important characteristic features by which the interference can be distinguished from the observed diffraction pattern.

Show, using a simple polaroid, that light waves are transverse in nature. Intensity of light coming out of a polaroid does not change irrespective of the orientation of the pass axis of the polaroid. Explain why.

In young’s double slit experiment, deduce the conditions for obtaining constructive and destructive interference fringes. Hence, deduce the expression for the fringe width.

Show that the fringe pattern on the screen is actually a superposition of slit diffraction from each slit.

What should be the width of each slit to obtain 10 maxima of the double slit pattern within the central maximum of the single slit pattern, for green light of wavelength 500 nm, if the separation between two slits is 1 mm?

Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays '1' and '2' are respectively 1.3 and 1.5. Trace the path of these rays after entering the prism.

Show, with the help of a diagram, how unpolarised sunlight gets polarised due to scattering.

Two polaroids P₁ and P₂ are placed with their pass axes perpendicular to each other. An unpolarised light of intensity I_o is incident on P₁. A third polaroid P₃ is kept in between P₁ and P₂ such that its pass axis makes an angle of 45° with that of P₁. Determine the intensity of light transmitted through P₁, P₂ and P₃

Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays '1' and '2' are respectively 1.35 and 1.45. Trace the path of these rays after entering the prism.

Using the phenomenon of polarisation, show how the transverse nature of light can be demonstrated.

Two polaroids P₁ and P₂ are placed with their pass axes perpendicular to each other. An unpolarised light of intensity I₀ is incident on P₁. A third polaroid P₃ is kept in between P₁ and P₂ such that its pass axis makes an angle of 30° with that of P₁. Determine the intensity of light transmitted through P₁, P₂ and P₃

Show, via a suitable diagram, how unpolarised light can be polarised by reflection.

Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of (a) reflected and (b) refracted light? Refractive index of water is 1.33.

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.

Draw a graph showing the variation of intensity (I) of polarised light transmitted by an analyzer with the angle (θ) between polariser and analyzer.

What is the value of refractive index of a medium of polarising angle 60°?