The angle of incidence at which reflected light is totally polarized for reflection from air to glass (refractive index $$n$$) is :

The binding energy per nucleon of deuteron $$\left( {{}_1^2\,H} \right)$$ and helium nucleus $$\left( {{}_2^4\,He} \right)$$ is $$1.1$$ $$MeV$$ and $$7$$ $$MeV$$ respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

A piece of copper and another of germanium are cooled from room temperature to $$77K,$$ the resistance of

The work function of a substance is $$4.0$$ $$eV.$$ The longest wavelength of light that can cause photo-electron emission from this substance is approximately.