Question

In the total electromagnetic energy falling on a surface is $U$, then the total momentum delivered (for complete absorption) is

• A. $ \frac{U}{c} $
• B. $ cU $
• C. $ \frac{U}{{{c}^{2}}} $
• D. $ {{c}^{2}}U $
• E. $ \sqrt{\frac{U}{c}} $

Answer 1

Answer: (A)

The object gains an energy $ \Delta U $ from radiation. Maxwell showed that the object also gains linear momentum, the magnitude
$ \Delta p $ or the change in momentum of the object is related to the energy change U by
$ \Delta p=\frac{U}{c} $