When the electron orbiting in hydrogen atom in its ground state moves to the third excited state, the de-Broglie wavelength associated with it

If 'E' and 'L' denote the magnitude of total energy and angular momentum of revolving electron in $n^{th}$ Bohr orbit then

Two different radioactive elements with half lives $T_1$ and $T_2$ have undecayed atoms $N_1$ and $N_2$ respectively, present at a given instant. The ratio of their activities at this instant is