The waves having maximum wavelength among the following electromagnetic waves is

If the de-Broglie wavelength of an electron is 2 nm , then its kinetic energy is nearly (Planck's constant $=6.6 \times 10^{-34} \mathrm{Js}$ and mass of electron $=9 \times 10^{-31} \mathrm{~kg}$ )

The ratio of the wavelengths of the spectral lines emitted due to transitions $3 \rightarrow 2$ and $2 \rightarrow 1$ orbits in the hydrogen atom is