Question

Which of the following is true?
A. The sound wave and the light waves both are longitudinal waves.
B. Both the sound and light waves are transverse.
C. In air, the sound waves are longitudinal as well as transverse.
D. In air, the sound waves are longitudinal and the light waves are transverse.

Answer 1

Hint: Sound wave is a pressure wave and light wave is electromagnetic wave. Obtain the properties of the pressure wave and the electromagnetic wave. Compare the properties and find the required answer to the question.

Complete step by step answer:
A longitudinal wave is a wave which oscillates in the direction of the sound wave. A transverse wave is a wave which oscillates in the perpendicular direction of the wave.
Sound waves can also be called the pressure wave. Sound wave is created due to vibration of any object. When an object vibrates, it creates vibration in the surrounding medium which creates sound waves. The particle in the medium moves in the direction of the wave and in the direction opposite to the direction of the wave. The same particles are compressed and expanded in the medium which carries the sound wave. Since, the particle in the medium of the propagation of the sound waves moves in the direction of the sound wave, sound wave is a longitudinal wave.
A light wave is an electromagnetic wave. A light wave or an electromagnetic wave have electric and magnetic field components which are in the perpendicular direction to each other and both are in the perpendicular direction to the direction of motion of the light wave. So, the components of the light waves move in the perpendicular direction of the light wave. So, we can say that light waves are transverse waves.

So, the correct answer is “Option D”.

Note:
For a transverse wave, the particles in the medium of propagation of the transverse wave moves in the perpendicular direction of motion of the wave. For longitudinal waves, the particles in the medium of propagation move in the same direction to the direction of motion of the wave.