The energy of light is 2.84 x 10 ^ -19 J. What is the wavelength?

Question

The energy of light is 2.84 x 10 ^ -19 J. What is the wavelength?



Answer 1

Hello, Zanea,

We will use the equation that relates a photon's energy with it's wavelength.

E = hc/v, where

E is the energy (in Joules for this problem)

h is Plank's constant (6.63x10^-34 J-sec)

c is the speed of light (3.00x10⁸ meters/sec), and v is the wavelength (meters in this problem).

We want the wavelength, v, so rearrange the equation to make solving it easier:

v = hc/E

v = (6.63x10^-34 J-sec)*(3.00x10⁸ meters/sec)/(2.84x10^-19J)

Joules and seconds cancel, leaving meters.

I get 6.99x10^-7 meters. This is a correct answer, but wavelengths are typically reported in nanometers, nm. It sounds more impressive and saves everyone the pain of exponents.

1nm = 10^-9 meter

(6.99x10^-7 meters/10^-9 meter/nm) = 699 nm

Bob