electromagnetic-waves Question 6
Question: Q. 2. Professor C.V. Raman surprised his students by suspending freely a tiny light ball in a transparent vacuum chamber by shining a laser beam on it. Which property of EM waves was he exhibiting? Give one more example of this property?
U] [SQP II 2017; NCERT Exemplar]
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Solution:
Ans. The properties of electromagnetic waves are similar to other waves as it carry both energy and momentum due to which it exerts radiation pressure. A tiny ball can be suspended freely in a transparent vacuum chamber by shinning a laser beam on it as electromagnetic wave exerts radiation pressure. Also, according to him, the tails of the comets are due to radiation pressure. 1
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[II Q. 3. In which directions do the electric and magnetic field vectors oscillate in an electromagnetic wave propagating along the $x$-axis ?
U] [Outside Delhi III 2017]
Ans. $\vec{E}$ along $y$-axis and $\vec{B}$ along $z$-axis
(Alternatively: $\vec{E}$ along $z$-axis and $\vec{B}$ along $y$-axis) 1
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Detailed Answer :
Theelectric and magneticfieldsin an electromagnetic wave oscillate along directions perpendicular to the direction of propagation of the wave. The direction of propagation of the electromagnetic wave is given by vector product of electric field and magnetic field,
$$ (E \hat{j} \times B \hat{k})=E B \hat{i} $$
If the wave propagation vector is along the $x$-axis, then the electric field vector is along $y$-axis and magnetic field vector is along $z$-axis.
OR
40 Electric and magpetic field vectors are perpendicu. las to the derection of popogatsin of the waves
The ecetric freld vector is along posctice $V$ axis
and ebe magnetic fecld is ofgiclaling along ebe positive zaxis. so chat $\left(F^{\prime} \times B\left(c^{\prime}\right)=E B C^{\lambda}\right.$. the wave is propogating along the tue $x$ axis.
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