Question

Since many wavelengths of light are measured in nanometers, it's useful to know that planck's constant (h) multiplied with the speed of

light (c) is equal to 1240 eVnm.
This is useful, as E = hf, or otherwise written as E= .
With this information in mind, solve the following:
A photon has 1.6 eV of energy. What is the wavelength of this photon?
O a
410 nm
Ob
775 nm
Ос
1984 nm
Od
306 nm

Answer 1

E = h f and since f = c / λ we have E = h c / λ

Thus λ = h c / E

Also, 1 ev = 1.6E-19 C

λ = 6.63E-34 * 3.0E8 / (1.6 * 1.6E-19)

λ = 6.63 * 3.0 / (1.6 * 1.6) * E-7

λ = 7.77E-7 = 777 nanometers

(B) is correct