(i) What is mean by reflection of sound?

Explanation

When sound waves travel in a given medium and strike the surface of another medium, it can be bounced back into the first medium is called as reflection
(ii) Explain the refraction at the boundary of a rarer and denser medium?
(a) Reflection in rarer medium
• Consider a wave travelling in a solid medium striking on the interface between the solid and the air.
• The compression exerts a force F on the surface of the rarer medium. • As a rarer medium has smaller resistance for any deformation, the surface of separation is pushed backwards. . As the particle of the rarer medium are free to move, a rarefaction is produced at the interface. Thus, a compression is reflected as a rarefaction and the rare faction travels from right to left.
(b) Reflection in denser medium: Incident Wave
• A longitudinal wave travels in a medium in the · form of compressions and rarefactions.
• Suppose a compression travelling in air from left to right reaches a rigid wall. • In turn, the wall exerts an equal and opposite reaction R--Fon the air molecules. This results in a compression near the rigid wall.
• Thus, a compression travelling towards the rigid wall is reflected back as a compression. That is the direction of compression is reversed.