A ship sends a sonar wave to the sea bed which is flat and measured several times over a large area. One day the reflected sound wave takes longer than in previous measurements. The possible reason is.
A. The frequency of the sonar wave, generated by the equipment is lower than previous measurements.
B. There is a solid object of large size in the path of the sonar wave.
C. There is a huge air bubble in the path of the sonar wave.
D. The loudness of sonar waves, generated by the equipment is lower than previous measurement.

Hint: Sonar wave amplitude falls in the air and takes longer to enter.To move faster in solids, sound, that is simply the collective collisions of particles. So, to reiterate, sound moves in solids the maximum, then water, then in air the slowest.

Complete step by step answer:
Sonar: Sonar is a process by which the distance and position of underwater artefacts are sensed and determined by acoustic means. The sonar apparatus senses sound waves produced from or absorbed from the target and analyses them for the information they provide.

Sound wave reflection also contributes to echoes. Echoes are unlike reverberations. Echoes happen when, more than 0.1 seconds after the initial sound wave has been detected, a mirrored sound wave enters the ear. The shape of the surface also influences the reflection in sound waves across surfaces.

Sound moves in solids the quickest and air the slowest. In between, there's water. It's because solid particles remain closer together rather than oil or gas particles, and solvent particles are closer together rather than gas particles. The heavier particles are concentrated in a space, the more often they collide.

Therefore, there must be a huge air bubble in the path of the sonar wave.

So, the correct answer is “Option C”.

Note:
In this question we have to determine why the reflected sound wave of sonar takes longer time. Echoes are indeed the sound reflected back to your ears from your own voice. Just after the band has ceased performing, the sound you hear echoing in an auditorium is created by reflecting off the walls as well as other objects. A sound wave can continue to echo, or reverberate, across a room until all the energy has been lost.