1) When sound (or any wave) is incident on a barrier where the nature of the medium changes (e. g. air to water) what generally happens?

A. All the energy is reflected

B. The sound is always completely absorbed

C. All the energy is transmitted

D. Energy is transmitted and reflected

2) Sound waves carry energy expressed as intensity I = (power/Area) averaged over time. How does intensity depend on the amplitude of the pressure oscillations, P0?

A. I∝P0

B. I∝1/P0^2

C. I∝P0^2

D. I is independent of P0

E. I∝P0^4

a) E (energy is transmitted and reflected) b) c I intensity is directly proportional to Po^2

Explanation:

Matter is not transfered during wave propagation only energy is transfered. An example is the light that passes through the pane of our window, bulk of the light passes through the pane but we also see the reflection of ourselves through the pane of the window showing transmission and reflection. Similarly, in sound wave the concept of echo follows this principles, we hear the reflected sound from the wall opposite the place of propagation and in the case where the place is not well padded part of the sound wave will be transmitted to the bodies or absorbed by the materials present.

b) using the formula:

I = ∆p2 / (2*density*v) where

I represent intensity (W/m^2), ∆p = pressure amplitude (Pa), density in kg/m^3 and V = wave speed in m/s, it is obvious that I varies directly to the square of the amplitude of the pressure of oscillation.