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

An e.m. wave exerts pressure on the surface on which it is incident. Justify.

Electromagnetic waves with wavelength

1. λ₁ is suitable for radar systems used in aircraft navigation.
2. λ₂ is used to kill germs in water purifiers.
3. λ₃ is used to improve visibility in runways during fog and mist conditions.

Identify and name the part of the electromagnetic spectrum to which these radiations belong. Also arrange these wavelengths in ascending order of their magnitude.

Identify the electromagnetic wave whose wavelength range is from about 10^-12 m to about 10^-8 m. Write one use of this.

Identify the electromagnetic wave whose wavelength range is from about 10^-3 m to about 10^-1 m. Write one use of this.

Choose the correct option related to wavelengths (λ) of different parts of the electromagnetic spectrum.

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.

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

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.

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

Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.

You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason

You are given three lenses of power 0.5 D, 4 D, and 10 D to design a telescope.

1) Which lenses should be used as objective and eyepiece? Justify your answer.

2) Why is the aperture of the objective preferred to be large?

An equiconvex lens of focal length 'f' is cut into two identical plane convex lenses. How will the power of each part be related to the focal length of the original lens ?

A double convex lens of + 5 D is made of glass of refractive index 1.55 with both faces of equal radii of curvature. Find the value of its radius of curvature.

Draw a ray diagram showing the image formation of a distant object by a refracting telescope ?

Write the two important factors considered to increase the magnifying power?

Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope ?

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

Define its magnifying power and write the expression for it?