Question

1.      Which of the following statements about electromagnetic waves in free space are true? (There could be more than one correct choice.)

		The electric field carries more energy than the magnetic field.
		The electric and magnetic fields have equal amplitudes.
		The electric field carries the same mount of energy as the magnetic field.
		The frequency of the magnetic field is the same as the frequency of the electric field.
		The frequency of the electric field is higher than the frequency of the magnetic field.

Answer 1

(a) In an electromagnetic wave, the energy associated with the electric field is equal to the energy associated with the magnetic field.

 Hence, option (a) is false.

 (b)

 The electric field and magnetic field are related as follows.

 E=cB

 Since the electric field is multiple of the speed of light and magnetic field.

 Therefore, the amplitude of the electric field is more than the amplitude of the magnetic field. Hence, option (b) is false.

(c)

 In an electromagnetic wave, the energy associated with the electric field is equal to the energy associated with the magnetic field

 Hence, option (c) is true.

(d)

 In an electromagnetic wave, the electric and magnetic field vectors are perpendicular to each other and oscillates in the direction perpendicular to the direction of propagation. The change in electric field and magnetic field occurs at the same time. Thus, they oscillate with the same frequency.

 Hence, option (d) is true.

(e)

 In an electromagnetic wave, the electric and magnetic field vectors are perpendicular to each other and oscillate in the direction perpendicular to the direction of propagation. The change in electric field and magnetic field occurs at the same time. Thus, they oscillate with the same frequency.

 Hence, option (e) is false.