Waves

Question 1

Assuming S is a pt source, derive the eqn in terms of P and r for the intensity I, at a pt dist r away from it

Answer 1

Intensity I at a pt is the energy per unit time per unit area transported normally thro a surface by a wave. Since S is a pt source, energy is transmitted radially and equally in all directions. The SA thro which energy is transported is spherical, centred at the source. hence, area = 4πr^2. Thus, I= Power of source/(2πr^2) (derived)

Question 2

eqn for phase diff (2)

Answer 2

Φ = x/λ (2π)
Φ = t/T (2π)

Question 3

Eqn for speed of a progressive wave

Answer 3

v=fλ