If the energy of a photon is 1.32 × 10¯18 j, what is its wavelength in nm? a. 1.50 × 10¯7 nm b. 150. nm c. 1.99 × 1015 nm d. 1.99 × 1024 nm e. none of these choices is correct.

A

Explanation:

The energy E of a photon is

directly proportional to its frequency f by E = hf, where h is Planck's constant (above)

and the wavelength w is inversely proportional to the frequency by w = c/f, so we have

E related to w by: E = hc/w. Since h and c are constants, their product hc is constant

being 1.989 * 10**-25 joule-meters. So if we know E is 1.32 * 10**-18 J, we have:

1.32 * 10**-18 = (1.989 * 10**-25) / w or w = (1.989 * 10**-25) / (1.32 * 10**-18) Doing

the division and we find w = 1.507 x 10-7 meters, or 150.7 nanometers. (ultraviolet)

A. 150 x 10-7nm