International Day Of Light | May 16
(Last Updated On: May 15, 2023)


Every year on May 16th, the International Day of Light promotes awareness for the appreciation of light and the role it plays in science, art, education, and sustainable development. The day also recognizes the natural benefits of light, as well as its many technological applications.


Even though everyone knows what light is, it can be hard to define. Light is not just the opposite of darkness. It is electromagnetic radiation within the electromagnetic spectrum that is perceived by the human eye. Visible light has wavelengths between 400 and 700 nanometers. Another way to define light is a stream of photons that travel with wavelike properties at the speed of light.

While we perceive the world in many ways, light is one of the most significant ways we comprehend the world around us. Additionally, light energy comes in many forms including visible light, infrared waves, ultraviolet light, gamma rays, and radio waves. According to Audrey Azoulay, the director-general of UNESCO, the understanding of light allows us to achieve the greatest of scientific and technological progress.

Here are just a few of the many applications that light is used for:

  • Lights are used to illuminate spaces, such as homes and offices.
  • UV lights are used in phototherapy to treat certain illnesses.
  • Ultraviolet energy is used to eradicate bacteria and viruses from the air and water.
  • Light is used in optical fiber networks, which helps to transmit information.
  • Lights are essential for safety, such as headlights for vehicles and traffic lights.
  • They are used in many household items, such as television sets, microwaves, and cell phones.
  • Natural light helps plants grow and provides many health benefits to humans.

It seems that every part of our lives are affected by light in some way.


Worldwide events to celebrate this day include light festivals that feature entertaining optic demonstrations, scientific lectures, and photo contests. To participate:

  • Think about the ways you benefit from light and how it helps you in your everyday life.
  • Do some fun light activities with your kids, such as making a periscope or a rainbow.
  • Watch science videos about light.

Share cool photos of light on social media. When you do, be sure to use #InternationalDayOfLight or #IDL.


Due to the success of the International Year of Light and Light-based Technologies 2015, UNESCO decided to organize a day dedicated to light. The first official International Day of Light was held on May 16th, 2018. The date May 16th marks the anniversary of the first successful operation of the laser. American physicist and engineer, Theodore Maiman is credited for inventing the laser. He fired the first laser in 1960.

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