(3-19)  Nefertiti has a powerful CO2 laser which she uses for cutting through steel. It has a power of 10 kW and operates in the infra-red, at a wavelength of 10.6 μm.

What we want to know is: if she were to direct this laser at Cormorant (whose mass is 2.5 kg) as he was flying away from her (with some urgency), and irradiate him for 5 seconds, how much might we expect his flight velocity to increase? We’ll assume that Cormorant has been treated with a totally reflective coating, so that all of the photons Nefertiti aims at him will bounce harmlessly off (even so, Cormorant would like it clearly established that this is just a Gedankenexperiment).

①  First let’s figure out how many photons are going to arrive in this laser burst. This means finding both the total energy delivered and the energy per photon and doing the division .

(Planck's constant, h = 6.63 x 10-34 Js)

②  Now see if you can calculate the momentum carried by each photon and hence the total momentum that could be transferred to Cormorant. Remember to take account of the reversal in direction of travel of each photon, when calculating the momentum change.

③ Hence deduce how much extra speed Cormorant needs to brace himself for.