An entrepreneur has proposed sending a probe to Alpha Centai 4light years away. His idea is to use a \"solar sail\", which is alarge area reflective sheet, and propelling the spacecraft to 10%of the speed of light using a high powered laser. If the lasersends 1200 nm light at the sail and the power reaching thereflective sheet is 1500 W:
(a) What is the force due to light pressure on the reflectivesheet, assuming the light backscatters with 20% efficiency?
(b) If an engineer is testing the spacecraft far away from thesolar system so that the gravity of the sun and planets can beignored, and the spacecraft is 65 kg, what would be the powernecessary to achieve 10% of the speed of light if the accelerationpart of the journey was only 5.0 x 10^5 km? (ignore relativisticeffects)
