Dr. Justin Dressel, assistant professor of physics at Chapman University’s Schmid College of Science and Technology, was recently featured on WAMC’s The Academic Minute explaining, “how quantum physics has a lot to do with what shows up on your screen.”

If you missed the live broadcast of Dressel’s The Academic Minute, its audio & transcript can be found below (courtesy of AcademicMinute.org).


Picture of Justin Dressel, Assistant Professor of Physics at Chapman University

Justin Dressel, Assistant Professor of Physics at Chapman University

During a candle-lit dinner a camera clicks: an intimate moment has been captured. The lighting is dim, the exposure brief. Little light sneaks past the shutter. On inspection, the photo is grainy, like static on an old television set.

But why?

If light were like waves at the beach or sound waves in the air, it could have any brightness, or, more precisely, dimness. A candle-lit photo would still be dim, but it would not be so grainy. The light level would vary smoothly, like gradually lowering a dimmer switch on the wall from brightness to total darkness, including every dimness in between. The dim light would cover the whole photo smoothly, keeping detail intact, even if difficult to see.

But light is not a simple wave. The dimmer switch for light is not smooth, but jumps in small steps from one brightness to the next. Each click of Nature’s dimmer switch for light has a name: one quantum of light, also called a photon. A quantum is one of a quantity, one discrete unit, and lies at the heart of quantum physics.

How do these quanta affect your camera? A digital camera image is gridded into millions of pixels. In bright light these megapixels collect billions of photons, making the discreteness of light nearly invisible, much like the grains of sand composing a sand dune. However, in dim light the pixels collect relatively few photons, which arrive at random times and at random locations. Detail is lost and the image becomes grainy, with spots of bright and dark where photons have and have not yet appeared.

So, you can thank quantum physics for making your digital photos grainy.