Recapping the Planck Formula

Remember Light, gamma rays, microwaves etc are all electromagnetic waves. An electromagnetic wave is made up a stream of particles called photons. Each photon has no mass but has a fixed amount of energy. The energy of the photon depends on the frequency of the light

Remember The energy of a photon = planck’s constant (H) x the frequency of the light(f)

Using the formula The value of Plank’s constant is 6.63 × 10-34 m2 kg s-1 Blue light of a frequency 6.00 x 1014 Hz is composed of a stream of photons What is the energy of each photon? Using E=hf E = 6.63 x 10-34 x 6.00 x 1014 E = 6.63 x 6.00 x 10-20 E = 3.98 x 10-19J

Using the formula The value of Plank’s constant is 6.63 × 10-34 m2 kg s-1 Microwaves in a microwave oven are composed of a stream of photons What is the energy of each photon if the microwaves have a frequency of 2450MHz? Using E=hf E = 6.63 x 10-34 x 2450 x 106 E = 6.63 x 2450 x 10-28 E = 1.62 x 10-24J

Using the formula The value of Plank’s constant is 6.63 × 10-34 m2 kg s-1 A particular gamma ray has a frequency of 5.00 x 1022 What is the energy of each photon? Using E=hf E = 6.63 x 10-34 x 6.00 x 1022 E = 6.63 x 6.00 x 10-12 E = 3.98 x 10-13J

Energy and photons E = 3.98 x 10-19J E = 1.62 x 10-24J The photons which make up the light have increasing energy as the frequency becomes greater

Wavelength If you are given the wavelength of the light rather than the frequency you use the wave formula c=λf to find the frequency of the light first. What is the energy of photons of red light with a wavelength of 700nm? Use this in the normal way in E=hf to find the energy of the photons.