× – J Energy of one mole of photons = ( . × – J) × ( . × mol – ) = . kJ mol – Problem .
A watt bulb emits monochromatic light of wavelength nm. Calculate the number of photons emitted per second by the bulb. Power of the bulb = watt = J s – Energy of one photon E = h ν = h c/ λ = . J s m s m = .
× – J Number of photons emitted J s J s . . Problem . When electromagnetic radiation of wavelength nm falls on the surface of sodium, electrons are emitted with a kinetic energy of .
× J mol – . What is the minimum energy needed to remove an electron from sodium? What is the maximum wavelength that will cause a photoelectron to be emitted? The energy ( E ) of a nm photon is given by = .
× – J The energy of one mole of photons = . × – J × . × mol – = . × J mol – The minimum energy needed to remove one mole of electrons from sodium = ( .
– . ) J mol – = . × J mol – The minimum energy for one electron This corresponds to the wavelength = c = . J s .
m s . J h E = nm (This corresponds to green light) Problem . The threshold frequency ν for a metal is . × s – .
Calculate the