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

Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.

Identify the part of the electromagnetic spectrum which:

1. produces the heating effect.
2. is absorbed by the ozone layer in the atmosphere.
3. is used for studying crystal structure.

Write any one method of the production of each of the above radiations.

A ray PQ incident normally on the refracting face BA is refracted in the prism BAC made of material of refractive index 1.5. Complete the path of ray through the prism. From which face will the ray emerge? Justify your answer.

Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.

Why can’t we see clearly through fog?

Name the phenomenon responsible for it.

A ray PQ incident on the refracting face BA is refracted in the prism BAC as shown in the figure and emerges from the other refracting face AC as RS such that AQ = AR. If the angle of prism A = 60° and refractive index of material of prism is `sqrt3 `. Calculate angle θ.

Why does unpolarised light from a source show a variation in intensity when viewed through a polaroid which is rotated?

Explain the basic differences between the construction and working of a telescope and a microscope

A ray PQ incident on the face AB of a prism ABC, as shown in the figure, emerges from the face AC such that AQ = AR.

Draw the ray diagram showing the passage of the ray through the prism. If the angle of the prism is 60° and refractive index of the material of prism is `sqrt3` , determine the values of angle of incidence and angle of deviation

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 1.38 and 1.52. Trace the path of these rays after entering through the prism.

A compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at

1. the least distance of distinct vision (25 cm), and
2. infinity?

What is the magnifying power of the microscope in each case?

1. A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece of focal length 1.0 cm is used, what is the angular magnification of the telescope?
2. 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 3.48 × 10⁶ m, and the radius of lunar orbit is 3.8 × 10⁸ m.

Use the mirror equation to deduce that an object placed between the pole and focus of a concave mirror produces a virtual and enlarged image.

You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct a compound microscope?

Define resolving power of a microscope and write one factor on which it depends

Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope has short focal lengths? Explain.

Why should the objective of a telescope have large focal length and large aperture? Justify your answer. 

When are two objects just resolved? Explain.

How can the resolving power of a compound microscope be increased? Use relevant formula to support your answer.