Buds Public School, Dubai
NAME: PHYSICS GRADE-12
Topic –Electromagnetic Waves
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1. How are infrared waves produced? Why are these referred to as 'heat waves' ?
Write their one important use.
2.
3. Name the constituent radiation of electromagnetic spectrum which
(a) Is used in satellite communication.
(b) Is used for studying crystal structure.
(c) Is similar to the radiations emitted during decay of radioactive nuclei?
(d) Has its wavelength range between 390 nm and 770 nm.
(e) Is absorbed from sunlight by ozone layer.
(f) Produces intense heating effect.
4. Write two applications each of (i) microwaves, (ii) infrared waves, and (iii) radio waves.
5. Name the radiations of electromagnetic spectrum which are used in
(a) warfare to look through fog.
(b) radar and geostationary satellites.
(c) studying the structure and properties of atoms and molecules.
6 .Name the following constituent radiations of electromagnetic spectrum which
(i) produce intense heating effect.
(ii) is absorbed by the ozone layer in the atmosphere.
(iii) is used for studying crystal structure.
7. Arrange the following electromagnetic radiations in ascending order of their
frequencies :
(i) Microwave
(ii) Radio wave
(iii) X-rays
(iv) Gamma rays
Write two uses of any one of these.
8.(a) An em wave is travelling in a medium with a velocity vvi. Draw a sketch showingthe propagation of the em wave, indicating the direction of the oscillating electric andmagnetic fields.
(b) How are the magnitudes of the electric and magnetic fields related to the velocity of the em wave?
9. Show, by giving a simple example, how em waves carry energy and momentum.
(ii) How are microwaves produced? Why is it necessary in microwave ovens to select the frequency of microwaves to match the resonant frequency of water molecules ?
(iii) Write two important uses of infra-red waves.
10.
11.(i) Which segment of electromagnetic waves has highest frequency ? How are these waves produced ? Give one use of these waves.
(ii) Which em waves lie near the high frequency end of visible part of em spectrum?
Give its one use. In what way this component of light has harmful effects on humans?
12. How are em waves produced by oscillating charges?
Draw a sketch of linearly polarized em waves propagating in the Z-direction.
Indicate the directions of the oscillating electric and magnetic fields.
13. Write Maxwell’s generalization of Ampere’s Circuital Law. Show that in the processof charging a capacitor, the current produced within the plates of the capacitor isi = 0(dE/dt)where Eis the electric flux produced during charging of the capacitor plates.
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