IV 



EXPERIMENTS ILLUSTRATING THE CARRIAGE 

 OF MOMENTUM BY A BEAM OF LIGHT 



SEVERAL experiments have been made by Dr. 

 Barlow and the author to illustrate the carriage 

 of momentum by a beam of light, 1 and recently 

 Prof. Lebedew 2 has described an experiment 



N 



c 



\J 



showing the absorption of momentum by a gas 

 which absorbs light. I shall now describe these 

 experiments. 



(i) When a beam of light falls obliquely on an 



1 Phil. Mag. IX, 1905, p. 169 and p. 393. Nature, vol. 75, 

 Nov. 22, 1906, p. 90. 



2 Ann. derPhysik, Bd. 32, 1910, p. 411. 



52 



