20. A laser beam of intensity S and cross-sectional area A is completely absorbed by aparticle of ma
問題詳情
20. A laser beam of intensity S and cross-sectional area A is completely absorbed by aparticle of mass m for a period△t . What is the change in speed of the particle? (A)SA△t/ m c ； (B) SA△t /m ； (C) SA /mc ； (D) SA△t/ c ； (E) None.