Question

In an electromagnetic wave,
A. Power is equally transferred along the electric and magnetic fields.
B. Power is transmitted in a direction perpendicular to both the fields.
C. Power is transmitted along the electric field.
D. Power is transmitted along the magnetic field.

Answer 1

Hint:Electromagnetic waves are formed as a result of electric field and magnetic field. Both electric and magnetic fields are perpendicular to each other. And a resultant Electromagnetic wave is propagated in the transverse direction hence electromagnetic waves are called transverse waves. Thus the electric field, magnetic field and the resultant electromagnetic wave are perpendicular to each other.

Complete answer:

(i)The moving charged particle induces the changing magnetic field. According to Faraday’s law, this changing magnetic field will create an electric field perpendicular to it.

(ii) We know that power is the product of voltage and current. And it transmits in all directions. As current flows in the direction perpendicular to the magnetic field and the magnetic and electric fields are perpendicular to each other, power is also transmitted in the direction perpendicular to both the fields.

Hence, the correct option is B.

Additional information:
(i)Oscillating charged particles produce electric and magnetic fields. This electric and magnetic field are perpendicular to each other. And these fields are starting from the same point. Hence they are in phase to each other. Hence, it forms a transverse wave called an electromagnetic wave.
(ii)Electromagnetic waves travel with the velocity of light hence it cannot be deflected by both electric and magnetic fields.

(iii) The sound waves need a medium to travel from one place to another place. But electromagnetic waves do not need any medium to travel like sound waves.
(iv) As we know that the electromagnetic waves are transverse waves, it is measured by its amplitude. The highest point in the electromagnetic wave is called ‘crest’ and the lowest point is called ‘trough’.

(v) The electromagnetic spectrum can be divided into different regions based on the wavelength and frequency. The waves under certain frequency ranges are divided into microwaves, X-rays, gamma rays, IR rays, UV rays and visible spectrum.
(vi) The rays having the highest frequency are UV rays. As it has high frequencies, it has more energy. And the waves with the least frequency are radio waves. Radio waves have larger wavelength hence it doesn’t scatter most.

Note:Power does not have a definite direction to pass. So it gets transmitted along all the directions. As we know that the EM waves are perpendicular to both electric and magnetic fields, power is also transmitted in the direction of EM waves. Hence power is transmitted in perpendicular to both the fields as a resultant electromagnetic wave.