湖光山色

Example #1 Problem: a.) What is the energy of a single photon (in eV) from a light source with a wavelength of 400 nm? Solution: Use E = pc = hc/l. This gives anser in Joules, then multiply by eV to get answer in eV. 3.1 eV b.) If a 50 W laser emits 400 nm light, how many photons are emitted in 10 seconds? Solution: In 10 seconds, 500 Joules=500/ eV of photons are emitted. Dividing this total energy by the energy per photon gives the total number of photons. 1.01E21 -------------------------------------------------------------------------------- --------------------------------------------------------------------------------