Calculate the work function that requires a 475 nm photon to eject an electron of 1.25 ev.

The work function has the formula
E = h v

where
E is the energy
h is the constant
v is the frequency

Since the given is wavelength, we use the relationship between frequency and wavelength
v = c / λ
where
c is the speed of light
λ is the wavelength

So.
E = h c / λ
h = Eλ / c = 1.25 eV (475x10-9m) / (3x10^8 m/s)
h = 1.9792 x 10^-15

The work function is:
E = 1.9792 x 10-15 v