2. Here are two types of lasers: Laser A- 400nm, 10 mW (W=J/s); Laser B- 800 nm, 10 mW.(Assume that hc = 2 x 10-25 J.m)

(1) How many photons are included in 1 m of laser beam in each case?Which one has more photons? How many times?

(2) When the two lasers irradiate on a metal having the work function of 1 x 10^-19 J, which laser induces higher photoelectric current? Assume that weak forward bias is applied to collect all emitted electrons from the metal.

(3) When the two lasers irradiate on another metal with the work function of 3 x 10^-19 J,which laser induces higher photoelectric current?