Question

If any explosion takes place at the bottom of a lake, what type of shock waves in water will take place?
A) Longitudinal waves
B) Transverse waves
C) Both
D) None of the above

Answer 1

Hint: We need to understand what shock waves means before answering this question. Also, recall what are longitudinal waves and transverse waves. Understand how we can classify waves under either longitudinal waves or transverse waves.

Complete step by step solution:
First understand the meaning of shock waves.
Pressure waves that are created due to explosions or any phenomena that brings in a major change in pressure, such pressure waves are known as shock waves.
Now, let us recall the longitudinal waves and transverse waves.
Longitudinal waves are waves in which the particles of the medium vibrate parallel to the direction of the motion of the wave. These waves are also known as compression waves as they consist of alternate compressions and rarefactions. In the compression region, the particles of the medium are closest to each other while in the rarefaction region the particles of the medium are farthest from each other. In the region of compression the pressure is high whereas in the region of rarefaction the pressure is low. Examples of longitudinal waves include sound waves, ultrasound waves and so on.
Transverse waves are waves in which the oscillations occur perpendicular to the direction of propagation of the wave. In these waves there are alternate crests and troughs. The particle oscillates to maximum upward displacement known as crests and maximum lower displacement known as the trough. Examples of transverse waves are light waves, microwaves, radio waves and so on.
The transverse waves transfer mass along the length of its travel and there is no role of pressure in the travelling of a transverse wave. The longitudinal waves do not transfer any mass, the particles oscillate at their position and only transfer energy in the form of pulse. The longitudinal waves involve change in pressure and are therefore also known as pressure waves.
Now that we know about the longitudinal and transverse waves, we can classify shock waves under either of them.
The shock waves are also a kind of pressure waves as there is a change in pressure during the forming of shock waves. And thus, the shock waves are considered as longitudinal waves and not as transverse waves.

$\therefore $ Option $(A)$, longitudinal waves is the correct option.

Note: The transverse waves cannot propagate in a gas or liquid medium as there is no mechanism for the particles to oscillate perpendicular to the direction of propagation of the wave. This means, transverse waves cannot propagate inside the water but the ripples produced on the surface of the water are transverse waves and not longitudinal waves. Do not confuse between the waves inside and on the surface of the water.