Dear students , some important questions are porvided with answers of -Chapter 8 – Electromagnetic waves of class XII
1 mark questions —-
1) Write down ihe expression for velocity of an electromagnetic wave in free space .
2) According to Ampere’s circuital law , what is its limitation ?
3) Which experiment confirmed the existence of electro magnetic waves?
4) Write down the equation of Ampere- Maxwell law.
5) Out of four Maxwell’s equations, which equation establishes non existence of magnetic monopolc?
6) Cite the range of visible spectrum in terms of wave length.
7) Which radiation of electromagnetic spectrum has the shortest wave length?
8) Which part of electromagnetic spectrum carries heat energy?
9) Name the part of electromagnetic spectrum which is suitable for radar system used in aircraft navigation.
10) Name the part of the electromagnetic spectrum of wavelength 10¯² m and mention its one application.
11) The oscillating magnetic field in plane electro magnetic wave is given by
By = 8 x 10-6sin[2x 10 ¹¹t + 300πx ]T Find the wave length of the wave.
12) Reference to problem 11 write down the expression for the oscillating electric field.
13) Identify the electromagnetic radiation as per wavelength
i) 1mm ii) 10¯¹² m
14) Why are infrared radiations referred to as heat radiation also?
15) Name one radiation which is next to infrared radiation in
electromagnetic spectrum having shorter wave length.
16) From the following identify the electromagnetic waves having the (i)Maximum (ii) Minimum frequency
(i) Radio waves (ii) Visible light (iii) Gamma ray (iv) Microwaves
(v) Ultraviolet rays and (vi) Infrared rays
17) Give one use of ultraviolet radiation.
18) Name two gases which absorb infrared radiation.
19) Name one gas which absorb UV radiation.
2 marks questions —-
1) Sketch a schematic diagram depicting electric and magnetic fields for an electromagnetic wave propagating along the Z-direction. How is velocity related to ε0 and μ0 ?
2) Describe in brief the concept of displacement current.
3) Can we expect a magnetic field in space in absence of conduction current? – Explain in brief.
4) What is radiation pressure ? Why we do not feel radiation pressure when sunlight falls on us ?
5) Write down the four Maxwell’s equations.
3 marks questions —-
1. What are γ-rays? Give two important properties of γ-rays. Depict the range of wave length of γ-rays. 1+1+1=3
2. What are X-rays? Give two important properties and uses of X-rays.
3. What are micro waves? Explain the principle of a microwave oven.1+2=3
4. Establish Amperes Maxwell equation 3
5. Write down various uses of radio waves 3
6. Give some uses of ultra violet rays . How human can be protected from it ? 3