What is the energy of a 426 nm photon emitted from a light source?I came up with 2.822676 x 10 -22, but this is wrong. Answer in units of J.

2 Answers

ndnordic's profile pic

ndnordic | High School Teacher | (Level 2) Associate Educator

Posted on

The relationship between energy and frequency for light is given by the equation E = hf, where h is Planck's constant and f is the frequency of the photon in m/s.

In this problem you have the wavelength, 426 nm, but the frequency is 1/wavelength.   !/426 nm = 2.347 x 10^6 Hz. Planck's constant is 6.626 x 10^-34 J/s.  Multiplying the two values gives an answer of 1.555 x 10^-27 J of energy.


william1941's profile pic

william1941 | College Teacher | (Level 3) Valedictorian

Posted on

The energy of a photon is given by the expression h*c / L , where h is the Planck's constant, and c is the speed of light in m/s and L is the wavelength of the photon in meters.

In your question, you say the photon wavelength is 426 nm or 426*10^-9.

h is 6.626 * 10^-34 joule s

c is 2.998 * 10^8 m / s

The energy of the photon is 6.626 * 10^-34*2.998 * 10^8/ 426*10^-9

= 4.66* 10^-19 J

Therefore the solution is the energy of the required photon is 4.66* 10^ -19 J