A mixture of hydrogen atoms (in their ground state) and hydrogen like ions (in their first excited state) are being excited by electrons which have been accelerated by same potential difference V volts. After excitation when they come directly into ground state, the wavelengths of emitted light are found in the ratio 5 : 1. Then, find
a. the minimum value of V for which both the atoms get excited after collision with electrons.
b. atomic number of other ion.
c. the energy of emitted light.