NCERT Solutions for Chapter: Electromagnetic Waves, Exercise 3: SA

Show that the magnetic field $B$ at a point in between the plates of a parallel-plate capacitor during charging is $\frac{{\epsilon }_0{\mu }_{0}r}{2}\frac{dE}{dt}$ (symbols having usual meaning).

Electromagnetic waves with wavelength
(i) ${\lambda }_1$is used in satellite communication.
(ii) ${\lambda }_2$ is used to kill germs in water purifier.
(iii) ${\lambda }_3$ is used to detect leakage of oil in underground pipelines.
(iv) ${\lambda }_4$ is used to improve visibility in runways during fog and mist conditions.

(a) Identify and name the part of electromagnetic spectrum to which these radiations belong. Also, write one more application of each.

(b) Arrange these wavelengths in ascending order of their magnitude.

Show that average value of radiant flux density $‘S’$ over a single period $‘T’$ is given by $S=\frac{1}{2c{\mu }_0}{E_0}^2$.

You are given a $2 \mathrm{\mu F}$ parallel plate capacitor. How would you establish an instantaneous displacement current of $1 \mathrm{mA}$ in the space between its plates?

Show that the radiation pressure exerted by an electromagnetic wave of intensity $I$ on a surface kept in vacuum is $I/c$.

What happens to the intensity of light from a bulb if the distance from the bulb is doubled?

As a laser beam travels across the length of a room, its intensity essentially remains constant. What geometrical characteristic of LASER beam is responsible for the constant intensity which is missing in the case of light from the bulb?

Even though an electric field $\mathrm{E}$ exerts a force $\mathrm{qE}$ on a charged particle yet the electric field of an electromagnetic wave does not contribute to the radiation pressure (but transfers energy). Explain.