Which of the following statement is not correct
The force on a hemisphere of radius $1\, cm$ if a parallel beam of monochromatic light of wavelength $500\, nm$. falls on it with an intensity of $0.5\, W/cm^2$, striking the curved surface in a direction which is perpendicular to the flat face of the hemisphere is (assume the collisions to be perfectly inelastic)
If the energy of a photon is $10\,eV$, then its momentum is
In a dark room of photography, generally red light is used. The reason is