Show that the intensity i is the product of the energy density u (energy per unit volume) and the speed of propagation v of a wave disturbance; that is, show that i = uv. (b) calculate the energy density in a sound wave 4.82 km from a 47.5 kw siren, assuming the waves to be spherical, the propagation isotropic with no atmospheric absorbtion, and the speed of sound to be 343 m/s.

a)I= E/A  = energy per unit volume * speed of propagation

b)energy density= 51.82 * 10 ^-9 j / m ^2

c) Intensity, is the amount of power crossing unit area perpendicular to the direction of the flow.intensity is related as

                                            I =U * V

d) energy density = 3.59*10 ^-5 space per unit volume.

Explanation:

a)

I = E/A

multiplying num and den by u

I = (Ev) / (Av)= (E / (u)) * u

= energy per unit volume * speed of propagation

b)

energy density

= 50kw / surface area

= 51.82 * 10 ^-9 j / m ^2

a)

In describing any flow of energy through space,it is useful to talk in terms of the power crossing unit area perpendicular to the flow,this is the intensity, usually denoted by I

intensity, is the amount of power crossing unit area perpendicular to the direction of the flow.intensity is related as

                                            I =U * V

b)

energy density of a radio wave=50000 / 4p (480) ^3

=3.59*10 ^-5 space per unit volume.

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray