CBSE Class 12 - Physics - Electromagnetic Waves - Important Theory Questions (#cbsenotes)(#eduvictors)

Electromagnetic Waves

(Important Theory Questions)

1. Explain the inadequacy of Ampere's circuital law

2. Describe Hertz experiment to demonstrate the production of electromagnetic waves

3. Write the properties of electromagnetic waves.

4. Write any five electromagnetic waves in the order of decreasing frequency and write any two properties and uses of each

5. Deduce an expression for velocity of em waves in vacuum.

6. Establish the transverse nature of electromagnetic waves.

7. Compare the properties of electromagnetic waves and mechanical waves.

Very Short Questions (1 Mark)

8. The charging current for a capacitor is 0.25A. What is the displacement current across its plates?

9. Write the following radiations in a descending order of frequencies: red light, X–rays, microwaves, radio waves

10. How does the frequency of a beam of ultraviolet light change, when it goes from air into glass?

11. It is necessary to use satellites for long distance TV transmission. Why?

12. What is the role of ozone layer in the atmosphere?

Short Question (2 Marks)

13. Write the application of Infra-red radiations?

14. Which constituent radiation of the electromagnetic spectrum is used?
 (a) To photograph internal parts of human body.
 (b) For air aircraft navigation

15. IF the earth did not have atmosphere would its average surface temperature be higher or lower than what it is now?

16. Sky waves are not used in transmitting TV signals, Why? Suggest two methods by which range of TV transmission can be increased?

17. List the applications of Gamma rays.

Long Questions (4 Marks)

18. Answer the following questions:
(a) Long distance radio broadcasts use short-wave bands. Why?

(b) It is necessary to use satellites for long distance TV transmission. Why?

(c) Optical and radio telescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth. Why?

(d) The small ozone layer on top of the stratosphere is crucial for human survival. Why?

(e) If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?

(f) Some scientists have predicted that a global nuclear war on the earth would be followed by a severe 'nuclear winter' with a devastating effect on life on earth. What might be the basis of this prediction?