Quantized Energy of Light

What happens when electrons move between energy levels

Electromagnetic Radiation

All EM radiation travels at the Speed of Light, c.

c = 3.00 x 108 m/s = λν

Frequency, ν, is the number of waves per second. The unit is called a Hertz (Hz) and mathematically is

Since we don’t really have a unit for a wave, the unit for frequency is:

If all EM waves travel the same speed, then the higher the frequency, the smaller each wave is.

As Frequency , Wavelength (λ) .

QuantumThe smallest amount

(chunk, photon, etc.) of energy that can be released as EM radiation.

Energy is absorbed when an electron jumps up to a higher energy level and is released when it falls back down to a lower energy level.

Planck’s ConstantMax Planck’s theory of quantized energy comes

from the equation:E = hνE = amount of energy absorbed or released.h = Planck’s constant = 6.626 x 10-34 Js.ν = The frequency of EM radiation emitted or

absorbed. The unit is Hertz, s-1.When the units are multiplied together:

ExampleHow much energy is released when a photon of

red light with a frequency of 4.41 x 1014 s-1.

= 2.92x10-19 JNot very much energy in 1 photon of light, huh?

Example 2A photon of Orange light, with a wavelength

of 600nm is absorbed by an electron. How much energy is gained by the electron.

Since the photon data is given to us as a wavelength (nm), and the energy equation uses frequency (s-1) we have to convert wavelength to frequency using:

Finally, you can use E = hν.

PhotonsPhotons are packets of light energy with

specific energies. These energies correspond to specific frequencies of light.

A photon of red light will have a lower frequency, and thus less energy than a photon of blue light. This can be observed when looking at flames. Most people know that a blue flame is hotter than a red/orange flame.