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

"A telescope resolves whereas a microscope magnifies." Justify this statement ?

Define its magnifying power and write the expression for it?

A compound microscope uses an objective lens of focal length 4 cm and eyepiece lens of focal length 10 cm. An object is placed at 6 cm from the objective lens. Calculate the magnifying power of the compound microscope. Also calculate the length of the microscope.

A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of focal length 1.0 cm is used, find the angular magnification of the telescope. If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.42 × 10⁶ m and the radius of the lunar orbit is 3.8 × 10⁸ m.

Use the mirror equation to show a convex mirror always produces a virtual image independent of the location of the object ?

Calculate the speed of light in a medium whose critical angle is 30° ?

Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.

 Out of blue and red light which is deviated more by a prism? Give reason.

Give the formula that can be used to determine refractive index of materials of a prism in minimum deviation condition ?

Draw a ray diagram to show the working of a compound microscope. Deduce an expression for the total magnification when the final image is formed at the near point.

In a compound microscope, an object is placed at a distance of 1.5 cm from the objective of focal length 1.25 cm. If the eye piece has a focal length of 5 cm and the final image is formed at the near point, estimate the magnifying power of the microscope.

What type of wavefront will emerge from a (i) point source, and (ii) distance light source?

Trace the rays of light showing the formation of an image due to a point object placed on the axis of a spherical surface separating the two media of refractive indices n₁ and n₂. Establish the relation between the distances of the object, the image and the radius of curvature from the central point of the spherical surface.

Hence derive the expression of the lens maker’s formula.

Draw the labelled ray diagram for the formation of image by a compound microscope.

Derive the expression for the total magnification of a compound microscope. Explain why both the objective and the eyepiece of a compound microscope must have short focal lengths.

An equilateral glass prism has a refractive index 1.6 in the air. Calculate the angle of minimum deviation of the prism, when kept in a medium of refractive index `4sqrt(2)"/"5.`

How does the angle of minimum deviation of a glass prism vary if the incident violet light is replaced by red light?

For paraxial rays, show that the focal length of a spherical mirror is one-half of its radius of curvature.

When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the colour of light?

When a wave is propagating from a rarer to a denser medium, which characteristic of the wave does not change and why?

A point-object is placed on the principal axis of convex spherical surface of radius of curvature R, which separates the two media of refractive indices n1 and n2 (n2>n1). Draw the ray diagram and deduce the relation between the distance of the object (u), distance of the image (v) and the radius of curvature (R for refraction to take place at the convex spherical surface from rarer to denser medium.

Use the above relation to obtain the condition on the position of the object and the radius of curvature in terms of n₁and n₂ when the real image is formed.