Paragraph on “What causes sonic boom?” complete paragraph for Class 9, Class 10, Class 11 and Class 12

What causes sonic boom?

Nowadays, most people have heard the bang caused by an aircraft travelling at the speed of sound, but do you know why it occurs ?

Sound is caused by a disturbance which creates waves that emanate from the centre of the disturbance. These waves are sound waves. When these vibrations are picked up by the ear drum they are interpreted by the brain as noise. When someone is standing still and talking, you can hear what he says, even if you are directly behind him. This is because sound waves travel out in a regular, circular pattern from the speaker. If an object is moving, the pattern made by the sound waves it creates alters, and becomes more spherical.

When an aircraft is flying, sound waves move out in a series of spherical wave fronts behind it. As the aircraft approaches the speed of sound, noise builds up as the wave fronts become closer and closer together. The wave fronts are drawing together because the sound and the aircraft are travelling at almost the same speed. At 1,200 km (740 miles) per hour, the aircraft and the sound waves are travelling at the same speed (known as Mach I) and all the wave fronts converge. This causes a tremendous amount of pressure to be built up. It is a basic principle in physics that every action has an equal and opposite  reaction. This means that thy amount pressure built up behind Lie aircraft matched by the air pressure front of it. When the aircraft is flying at the speed of sound, the clash between the two areas of pressure is so intense that a violent shock wave occurs. This shock wave produces the loud bang that you hear on the ground.

Once the aircraft has accelerated  beyond the speed of sound, the wave fronts move away from each other, and the concentration of pressure is dispersed. When the aircraft slows down to the speed of sound again, another sonic boom will be heard.