Question: Q. 5. (i) 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?
(ii) Write two important uses of infrared waves.
U[ [Delhi Comptt. I, II, III 2014]
Show Answer
Solution:
Ans. (i) Microwaves are produced by special vacuum tubes like the Klystron / Magnetron / Gunn diode.
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The frequency of microwaves is selected to match the resonant frequency of water molecules, so that energy is transferred efficiently to the kinetic energy of the molecules.
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(ii) (a) Associated with the greenhouse effect. $1 / 2$
(b) In remote switches of household electrical appliances. [CBSE Marking Scheme 2014] 1/22
[AI Q. 6. Arrange the following electromagnetic radiations in ascending order to their frequencies :
(i) Microwaves
(ii) Radio waves
(iii) $X$-rays
(iv) Gamma rays
Write two uses of any one of these.
R[Delhi Comptt. I, II, III 2013, O.D. I, II, III 2010]
Ans. Radio waves $<$ Microwaves $<$ X-rays $<$ Gamma rays
Uses of Microwaves :
(i) Aircraft navigation,
(ii) Ovens.
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[CBSE Marking Scheme 2010-2013]
