Assume that sodium produces monochromatic light with a wavelength of 5.89×10−7 m. At what approximate rate would a 10 watt sodium-vapour light be emitting photons? Assume that the efficiency of the light bulb is about 30%.
a) 8.9×1018 photons/sec.
b) 3.0×1019 photons/sec.
c) 9.9×1019 photons/sec.
d) 2.0×1020 photons/sec.