Question

Out of the following the wave that cannot propagate in vacuum is:
1. Light waves
2. Radio wave
3. X-rays
4. Sound waves

Answer 1

Correct Answer - Option 4 : Sound waves

CONCEPT:

Electromagnetic waves or EM waves:

• The waves that are formed as a result of vibrations between an electric field and a magnetic field and they are perpendicular to each other and to the direction of the wave is called an electromagnetic wave.
• The accelerating charged particle produces an electromagnetic (EM) wave.
• A charged particle oscillating about an equilibrium position is an accelerating charged particle.
• Electromagnetic waves do not require any matter to propagate from one place to another as it consists of photons. They can move in a vacuum.

Properties of electromagnetic waves:

1. Not have any charge or we can say that they are neutral.
2. Propagate as a transverse wave.
3. They move with the velocity the same as that of light i.e 3 × 108 m/s.
4. It contains energy and they also contain momentum.
5. They can travel in a vacuum also.

EXPLANATION :

• From the given option except for sound, all others are electromagnetic waves.
• Sound requires a medium to travel hence it cannot go through a vacuum. Hence, option 4 is the answer