Hello,

Using Planck's expression

E=hxf

which is same as E=hc/λ

h is the "Planck Constant" which = 6.63×10^−34xJ.s

f is the frequency

c=3x 10^8 m/s

λ is the wavelength

hence E=6.63x 10^-34x3x 10^8/(3720x10^-10)=5.34x10^-19J

1 Joule of work is done when 1 Coulomb of charge is transported via a potential difference of 1 Volt.

The effort done in transporting one electron via a potential difference of one volt is measured in electron volts.

The charge on the electron is assumed to be in this case 1.6x10^-19 C

1eV=1.60×10^−19J

energy of photon in eV=5.34x10^-19J/1.60×10^−19J

=3.34eV

Hope you got it