Question

Answer the following
(a).Name the electromagnetic waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.
(b).If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.
(c).An electromagnetic wave exerts pressure on the surface on which it incident. Justify.

Answer 1

Hint: Different types of electromagnetic waves are used for different purposes according to their properties. For example, microwaves are used in radar systems for navigation, Infrared waves play an important role in maintaining earth’s temperature and ultraviolet waves are used in LASIK.
An electromagnetic wave carries energy and momentum with it.

Complete answer:
Electromagnetic waves are the waves produced by vibrations between electric and magnetic fields. They differ from all other waves in respect that they do not require any medium to travel. Electromagnetic waves are very useful in various natural processes. These are also being used in many devices like radar, TV for transmitting signals.
(a).Microwaves are used for radar systems used in aircraft navigation. Microwaves are short-wavelength radio waves produced by special vacuum tubes called klystrons, magnetrons, and Gunn diodes. Microwaves are best suitable for radar systems because of their shorter wavelengths. Their frequency range lies between ${{10}^{9}}-{{10}^{12}}$ Hz.

(b).The infrared rays of the sun keep the earth’s surface warm due to the greenhouse effect of the atmosphere. Greenhouse effect is a natural process of absorption of infrared waves that are reflected back by earth’s surface by greenhouse gases present in the atmosphere. If the earth did not have an atmosphere, its temperature would be lower than it is now. This process maintains the Earth’s temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist.

(c).According to Maxwell's theory of electromagnetism, an electromagnetic wave has linear momentum associated with it. If the total energy transferred to a surface on which incident in time $t$ is $U$, then the magnitude of the total momentum delivered to the surface for complete absorption is
$p=\dfrac{U}{c}$

Note:
Electromagnetic waves are produced by an accelerating charge. The frequency of electromagnetic waves is the same as that of an electric charge due to which it is produced.
The speed of electromagnetic wave in free space is constant and equal to the speed of light, $c=3\times {{10}^{8}}\text{ }m{{s}^{-1}}$