A $100 \mathrm{W}$ Lamp emits electromagnetic radiation in all directions. Assuming the lamp to be a point source Calculate the intensity of the radiation:

(b) At a distance of $2.0 \mathrm{m}$ From the lamp.

A wave from a source has an amplitude of $5.0 \mathrm{cm}$ and an intensity of $400{\mathrm{Wm}}^{-2}$.

(a) The amplitude of the wave is increased to $10.0 \mathrm{cm}$. Calculate the intensity now.

A wave from a source has an amplitude of $5.0 \mathrm{cm}$ And an intensity of $400{\mathrm{Wm}}^{-2}$.

(b) The intensity of the wave is decreased to $100 \mathrm{W}{\mathrm{m}}^{-2}$ Calculate the amplitude now.

An oscillator is used to send a transverse wave along a stretched string. The wavelength of the wave is $5.0 \mathrm{cm}$ when the frequency of the oscillator is $30 \mathrm{Hz}$. For this wave, calculate:

(a) Its frequency

An oscillator is used to send a transverse wave along a stretched string. The wavelength of the wave is $5.0 \mathrm{cm}$ when the frequency of the oscillator is $30 \mathrm{Hz}$. For this wave, calculate:

(b) Its speed.

Copy and complete Table 12.2. (You may assume that the speed of radio waves is $3.00\times {10}^8 \mathrm{m}{ \mathrm{s}}^{-1}$)

A plane's engine emits a note of constant frequency $120 \mathrm{Hz}$. It is flying away from a stationary observer at a speed of $80 \mathrm{m}{\mathrm{s}}^{-1}$. Calculate:

(a) The observed wavelength of the sound received by the observer