Question

A 32 W (1 W = 1 J/s) lamp generates violet light at a wavelength of 420 nm. How many photons of this light will the lamp generate in 2.0 s?

Answer 1

E/photon = hc/wavelength
E/photon = approx 5E-19 J but you should confirm that for a more accurate answer.
32W = 32 J/s * 2s = 64 J
Then 5E-19 J/photon x # photons = 64 J.
Solve ofr # photons.

Answer 2

I am a little confused on how you got 5E-19 J

Answer 3

The first two lines.
E = hc/wavelength
E = 6.626E-34 x 3E8/420E-9 = ? J/photon.