The energy of an electron in the ground state of hydrogen atom is -13.6 eV . The kinetic and potential energy of the electron in the first excited state will be

The potential energy between two nucleon's inside a nucleus is minimum at a distance of about

Assertion (A): An alpha particle is moving towards a gold nucleus. The impact parameter is maximum for the scattering angle of $180^{\circ}$.

Reason (R): The impact parameter in an alpha particle scattering experiment does not depend upon the atomic number of the target nucleus.

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