Light does not only behave as a wave — it also behaves as a particle.
This particle of light is called a photon.
Each photon carries a specific amount of energy. The amount of energy depends on the frequency of the light.
This concept explains many everyday phenomena such as:
Why ultraviolet light causes sunburn
Why red light is used in photographic darkrooms
How we see different colors
Understanding photon energy is important in fields such as photography, medicine, communication technology, and energy production.
Light energy is not continuous.
It is released in small packets called photons.
Has no mass
Travels at the speed of light
Carries a definite amount of energy
Energy depends on frequency
The energy of a photon is given by the equation:
Where:
E = energy of the photon
h = Planck’s constant
f = frequency of light
Higher frequency → Higher energy
Lower frequency → Lower energy
From lowest to highest energy:
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Within the visible spectrum:
RED → lowest energy
VIOLET → highest energy
Photographic films contain light-sensitive chemicals.
Red light has:
Low frequency
Low photon energy
Because of this, it does not activate the chemicals on the film.
This allows photographs to be developed without being ruined.
Ultraviolet light has:
Very high frequency
Very high photon energy
This high energy:
Damages skin cells
Causes sunburn
Can lead to skin diseases with long exposure
That is why protection from UV radiation is important.
White light contains all the colors of the visible spectrum.
Objects appear colored because they:
Absorb some wavelengths
Reflect certain wavelengths
The reflected light enters our eyes and is detected by cone cells in the retina.
Different wavelengths → different perceived colors
Each color has a different photon energy.
Sunscreen absorbs or blocks high-energy UV photons
Sunglasses protect the eyes from UV radiation
Darkroom red light prevents unwanted exposure
Light filters control photon energy reaching the film
Different colors produce different photon energies
Used in screens, indicators, and lighting systems
Medical surgery
Barcode scanners
Fiber-optic communication
Convert photon energy into electrical energy
Understanding light energy helps us:
Protect our skin and eyes
Use proper lighting for specific tasks
Develop modern technologies
Improve medical and communication systems
Light is made of photons.
Photon energy depends on frequency.
Higher frequency means higher energy.
Ultraviolet light causes sunburn because of high energy.
Red light is used in darkrooms because of low energy.
Color is determined by wavelength and photon energy.