What is a Photon? - Physics of Light
Welcome to Quatr.us Study Guides!

Photons

Sunshine

February 2017 - Photons are tiny little particles of light, far too small to see individually. All light is made of photons (FOE-tahns). The earliest photons probably appeared about fifteen billion years ago, during the Big Bang. Unlike electrons and quarks, photons have no mass, so they can travel at the speed of light (about 186,000 miles per second) - that's why we call it the speed of light.

Photons behave in some ways like particles, little bits of stuff, and in other ways like waves. It's not just visible sunlight that is made of photons, but a lot of other kinds of waves like radio waves, television broadcasts, x-rays, and the ultraviolet (UVA and UVB) rays that give you sunburns. The difference between light and these other kinds of waves depends on the size of the wave - the wavelength. Very short waves are x-rays and ultraviolet rays, that cause sunburn. Visible light like sunlight is made of medium-length waves. Radio and television waves are very long waves. But all of these rays are made of photons.


Showing that photons are particles

If a photon moves in short wavelengths, like x-rays or ultraviolet rays, then that photon has more energy. It's like if you were jumping rope quickly, you'd be using more energy than someone who jumped slowly. That's why you have to be careful how much x-ray radiation or UV rays you get, or you'll get radiation sickness or a sunburn. If the wavelength is longer, then that photon will have less energy - that's why it's not dangerous to stand in the way of microwaves, or cell phones, or radio or television broadcasts.

When photons bump into other atoms, some of their energy can get the electrons in those atoms moving faster than they were before - that's what we call heat. That's why you get hot sitting in the sun. (Microwaves work differently: they are long waves that hit water molecules just right to make them flip around, and it's the friction from the water molecules flipping that heats your food.)

Learn by Doing - Setting up a Solar Oven

Bibliography and further reading about light:

Heat
Atoms
Physics
History home


Celebrating Black History Month with the pharaoh Hatshepsut, the queen Shanakdakhete, the poet Phillis Wheatley, the medical consultant Onesimus, the freedom fighters Toussaint L'Ouverture, Denmark Vesey, Yaa Asantewaa, and Samora Moises Machel, and the civil rights leader Martin Luther King, Jr.
Please help other teachers and students find us: link to this page from your class page.
Karen Carr is Associate Professor Emerita, Department of History, Portland State University. She holds a doctorate in Classical Art and Archaeology from the University of Michigan. Follow her on Instagram or Twitter.
Cite this page
  • Author: K.E. Carr
  • Title:
  • Site Name: Quatr.us Study Guides
  • Publisher: Quatr.us
  • Date Published:
Proud of your class page, homework page, or resource page? Send it in and win a Quatr.us "Great Page!" award!
Sign up for more free articles and special offers in Quatr.us' weekly newsletter:
We will never share your e-mail address unless you allow us to do so. View our privacy policy. Easy unsubscribe links are provided in every email.
Comment on This Article

Cool stuff we've been enjoying: Looking for birthday gifts? Check out these new Chromebooks - all the computer you need for only $229.00!. Then study in peace with these Beats wireless headphones - for the exact same price! When you're done, show off your presentation or watch a movie with this excellent smartphone projector for only $39.99!


Does your class page honor diversity, celebrate feminism, and support people of color, LBGTQ people, and people with disabilities? Let us know, and we'll send you a Diversity Banner you can proudly display!
Looking for more?
ADVERTISEMENT
Quatr.us is loading comments...
(Comments will appear after moderation, if they are kind and helpful. Feel free to ask questions, and we'll try to answer them.)
Cite this page
  • Carr, K.E. . Quatr.us Study Guides, . Web. 27 February, 2017
ADVERTISEMENT