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Important questions for Class XII -Chapter 8 – Electromagnetic waves

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


Homework for XI/group A/SHIKSHA/Saturday/29-09-2018

Q1.  A force of 200 N is applied to a block of mass 20 kg on an inclined plane at 53 º with the horizontal .

(i)  What will be the acceleration of the block in downward direction ?

(II) How much force is required to move it in up along the plane ?

(iii) How much force is required to keep the body at rest on the inclined plane ?

Q2.  Write down some of the advantages and disadvantages of friction

Q3. A 20 kg block is initially at rest on a rough horizontal surface. A horizontal   force of 75 N is required to set the block in motion. After it is in motion, ahorizontal force of 60 N is required to keep the block moving  with constant speed. Find the coefficient of static  and kinetic friction .

Q4. A body of 5 kg weight kept on a rough inclined plane of angle 30º starts  sliding with a constant velocity. Then find the coefficient of friction . (assume  g = 10 m/s²)

Q5. Define the following terms

Sliding friction , limiting friction , angle of friction , coefficient of kinetic friction , angle of repose .

Homework for XII/group B/VIDYARTHI/Friday/28-09-2018

Q1. An AC is given as   i = 10 sin ωt  with .0.02 sec as time period . Draw the AC showing the mean value and RMS value .

Q2. Prove that mean value for the full cycle of an AC is zero .

Q3. The RMS voltage  of the power supply that we use in India is 220 volt . What will be it’s peak value ? Also find the mean value .

Q4. Why AC is dangerous ?

Q5.  An AC   i = 10 sin 314t  is connected to a resistor of resistance 10 Ω   . Find the potential drop across the resistor .

Q6.  An AC   i = 10 sin 314t  is connected to an inductor  of self induction of  10 Henry  . Find the potential drop across the inductor .

Q7.  An AC   i = 10 sin 314t  is connected to a capacitor of 10 μF   . Find the potential drop across the capacitorr .

Q8. Draw the graph showing the variation between

(I) inductive reactance and angular frequency

(ii) capacitive reactance and angular frequency

Homework for XI / group B / Vidyarthi /Friday?28-09-2018

Q1.  A force of 200 N is applied to a block of mass 20 kg on an inclined plane at 37 º with the horizontal .

(i)  What will be the acceleration of the block in downward direction ?

(II) How much force is required to move it in up along the plane ?

Q2.  The coefficient of friction for a block of mass 10 kg and a surface is  0.3 .  Find the force of friction and the acceleration of the block if the applied force is 10 N , 30 N , 50 N and 0 N .

Q3. Explain why

(i) rolling friction helps in motion

(ii) static friction is a self adjusting force

Q4. State the laws of friction

Q5. Define the following terms

Sliding friction , limiting friction , angle of friction , coefficient of kinetic friction , angle of repose .


Hello students!

I have started my new blog named physics , which was earlier the name of my website . Due to some technical issues I have to repair that website and in place of it , starting this blog to interact with you.

You can ask your questions and doubts . I will definitely try to give you the answer.

I regularly submit the home works for my different batches at my institution named VIDYARTHI and SHIKSHA .

Hope you will cooperate .


Tridib sir
dated 28th September 2018

Science & Physics

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