A beam of light travels from air into a medium. Its speed and wavelength in the medium are $$1.5 \times 10^8\mathrm{ms}^{-1}$$ and $$230 \mathrm{~nm}$$ respectively. The wavelength of light in air will be

Which one of the following metals does not exhibit emission of electrons from its surface when irradiated by visible light?

A hydrogen atom makes a transition from $$n=5$$ to $$n=1$$ orbit. The wavelength of photon emitted is $$\lambda$$. The wavelength of photon emitted when it makes a transition from $$n=5$$ to $$n=2$$ orbit is

The curve of binding energy per nucleon as a function of atomic mass number has a sharp peak for helium nucleus. This implies that helium nucleus is