EM Waves Problem 13: A light sail is a propulsion technique that uses large sails to catch light and propel a vehicle in the vacuum of space. In a particular application, an Earth based laser illuminates such a sail perpendicularly with a beam of light of frequency 590 THz while emitting 3.8 × 1041 photons per second. Part (a) If 80% of the emitted photons reach the sail and are absorbed by it, find the resulting force, in newtons, on a sail that is momentarily at rest with respect to the laser. Part (b) Now assume the photons are reflected by the sail. Keeping all the other assumptions of part (a), find the force the light beam exerts on the sail, in newtons. Part (c) Ideally it would be best to use photons provided by natural sources to push the sail. If a star emits ns photons per second uniformly in all directions, with all the photons of frequency fs, enter an expression for the force on the sail if all the photons that strike it are reflected. Assume that the sail has an area A, is located at a distance d from the star’s center, is perpendicular to the incoming photons, and is momentarily at rest with respect to the star. Form your expression in terms of the defined quantities, h (Planck’s constant), and c (the speed of light).
EM Waves
Problem 13: A light sail is a propulsion technique that uses large sails to catch light and propel a vehicle in the vacuum of space. In a particular application, an Earth based laser illuminates such a sail perpendicularly with a beam of light of frequency 590 THz while emitting 3.8 × 1041 photons per second.
Part (a) If 80% of the emitted photons reach the sail and are absorbed by it, find the resulting force, in newtons, on a sail that is momentarily at rest with respect to the laser.
Part (b) Now assume the photons are reflected by the sail. Keeping all the other assumptions of part (a), find the force the light beam exerts on the sail, in newtons.
Part (c) Ideally it would be best to use photons provided by natural sources to push the sail. If a star emits ns photons per second uniformly in all directions, with all the photons of frequency fs, enter an expression for the force on the sail if all the photons that strike it are reflected. Assume that the sail has an area A, is located at a distance d from the star’s center, is perpendicular to the incoming photons, and is momentarily at rest with respect to the star. Form your expression in terms of the defined quantities, h (Planck’s constant), and c (the speed of light).
Step by step
Solved in 2 steps with 2 images
