CBSE Class 12 · 2017 · Delhi · EM WavesVery Short Answer

The electromagnetic waves used to purify water are

Name the parts of the electromagnetic spectrum which are
(i) stopped by the face mask worn by welders,
(ii) used in the detectors in Earth satellites, and
(iii) used in the 'short-wave band' in communication. Also write the order of wavelengths in each case.

$\vec{E}$ and $\vec{B}$ represent the electric and magnetic fields of an electromagnetic wave respectively. The direction of propagation of the wave is along

How are infrared waves produced? Why are these waves referred to as heat waves? Give any two uses of infrared waves.

(a) (i) Arrange the following electromagnetic radiations in the ascending order of their frequencies: X-rays, microwaves, gamma rays, radio waves.
(ii) Write two uses of any two of these radiations.

(a) Write the expression for the speed of light in a material medium of relative permittivity ${\epsilon }_r$ and relative magnetic permeability ${\mu }_r$.
(b) Write the wavelength range and name of the electromagnetic waves which are used in (i) radar systems for aircraft navigati …