Question 1

Which relation correctly connects wave speed (c), frequency (f), and wavelength (λ) for an EM wave in vacuum?

Accepted Answer

c = fλ. For any wave, speed equals frequency times wavelength. For EM waves in vacuum, the speed is c, so c = fλ. If frequency increases, wavelength decreases when c is constant.

Question 2

In a plane electromagnetic wave, the electric field (E), magnetic field (B), and direction of propagation are?

Accepted Answer

Mutually perpendicular, with E and B both perpendicular to propagation. In an electromagnetic wave, E and B are at right angles to each other. Both fields are also perpendicular to the direction the wave travels. This shows EM waves are transverse.

Question 3

Which part of the electromagnetic spectrum has the longest wavelength?

Accepted Answer

Radio waves. Radio waves have the longest wavelengths in the EM spectrum. Long wavelength means low frequency for the same wave speed. Many communication systems use radio waves.

Question 4

Which electromagnetic radiation is commonly used in TV remote controls?

Accepted Answer

Infrared. Remote controls commonly use infrared radiation. Infrared lies just beyond the red end of visible light. It is also associated with heat radiation from warm objects.

Question 5

Which electromagnetic radiation has the highest frequency?

Accepted Answer

Gamma rays. Gamma rays have the highest frequencies in the EM spectrum. Higher frequency means higher photon energy. Gamma rays are strongly ionizing compared to visible light.

EM Waves — Set 1