🟩 INTRODUCTION

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.

🟦 THE PHOTON CONCEPT

Light energy is not continuous.
It is released in small packets called photons.

Key Properties of a Photon:

• Has no mass
  
  

• Travels at the speed of light
  
  

• Carries a definite amount of energy
  
  

• Energy depends on frequency

🟨 ENERGY–FREQUENCY RELATIONSHIP

The energy of a photon is given by the equation:

E = hf

Where:

E = energy of the photon
h = Planck’s constant
f = frequency of light

Important Relationship:

Higher frequency → Higher energy
Lower frequency → Lower energy

🟩 LIGHT IN THE ELECTROMAGNETIC SPECTRUM

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

🟦 WHY RED LIGHT IS USED IN DARKROOMS

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.

🟨 WHY ULTRAVIOLET LIGHT CAUSES SUNBURN

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.

🟩 HOW WE SEE COLORS

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

🟨 PRACTICAL APPLICATIONS

UV Protection

• Sunscreen absorbs or blocks high-energy UV photons
  
  

• Sunglasses protect the eyes from UV radiation
  
  

Photography

• Darkroom red light prevents unwanted exposure
  
  

• Light filters control photon energy reaching the film
  
  

LED Technology

• Different colors produce different photon energies
  
  

• Used in screens, indicators, and lighting systems
  
  

Lasers

• Medical surgery
  
  

• Barcode scanners
  
  

• Fiber-optic communication
  
  

Solar Panels

• Convert photon energy into electrical energy

🟩 IMPORTANCE IN DAILY LIFE

Understanding light energy helps us:

• Protect our skin and eyes
  
  

• Use proper lighting for specific tasks
  
  

• Develop modern technologies
  
  

• Improve medical and communication systems

🟥 SUMMARY

• 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.