(a)[2]
State the meaning of the term photon.
(b(i))[1]
A beam of light falls normally onto a metal surface, as shown in Fig. 8.1. The beam has cross-sectional area $1.3 \times 10^{-5}\,\text{m}^2$ and power $2.7 \times 10^{-3}\,\text{W}$. Its wavelength is $570\,\text{nm}$. The light energy is absorbed by the metal and no light is reflected. Show that one photon of this light has an energy of $3.5 \times 10^{-19}\,\text{J}$.
(b(ii).1)[2]
Calculate the number of photons incident on the surface in $1.0\,\text{s}$.
(b(ii).2)[3]
Calculate the change in momentum of the photons in a time of $1.0\,\text{s}$.
(c)[2]
Use your answer in (b)(ii) to calculate the pressure exerted by the light on the metal surface.