Convection Current Above Toaster

[MTbowels]

When there is bright sunlight coming through my kitchen window, I can "see" the heat emanating from my toaster against the white tiles on my kitchen wall. What exactly am I seeing? Am I seeing "heat" and why is it visible under these circumstances?
After all, none of us can normally see air moving, only its action such as all the grass moving in one direction in a field during a strong breeze. So what exactly are these convection currents made of above my toaster?

thanks

[woofgang]

do you mean heat shimmer?
http://www.komonews.com/news/archive/4083201.html

[Graham-W]

As the air in the toaster heats up, it expands and the angle of diffraction alters. This means that light passing through the heated air is diffracted at a different angle to cooler air. The fact that the cool air and hot air is mixing causes the light passing through to give a shimmering effect as the light passes through different densities of air.

[MTbowels]

yes, from the link description, this might well be the effect I'm seeing. Still, it doesn't exactly explain it.

[MTbowels]

Sorry but you've lost me in you're explanation Graham-W.

[jim360]

The heat shimmer is a similar effect to what you see on hot days over roads. I think graham's explanation is essentially the gist of it, though I think he means "refracted" rather than diffracted.

Light travels in straight lines in general but can be bent in an effect called "refraction" that occurs whenever a beam of light passes from one material to another. You can think of hot and cold air as different materials, so as light travels between regions of hotter and colder air it refracts. Because meanwhile the air is flowing (hot air rises and in so doing pushes the colder air out of the way) that means there's a lot of boundaries between the cold and the hot air for the light to refract through. That leads to the shimmering effect because of the complicated light paths and the ever-changing position of the hot and cold air.

[gen2]

Yes, you are just seeing density variations that are the result of heating air. You are not seeing heat itself.
You can see the density variations much clearer by using Schlieren photography.

[mibn2cweus]

Air density is inversely proportional to temperature. Warmer air is more energetic and pushes harder against adjacent molecules resulting in a greater distribution and lower density than that of the surrounding cooler air. Lower density results in a lower refractive index than that of the surrounding air so that light rays no longer move parallel as they do in air that is all of the same temperature.

[jomifl]

If the sunlight is shining through the air of mixinx refractive indices onto a surface behind the toaster you might get a moving pattern of dappling similar to the effect you get when the sun shines through ripples onto the bottom of a swimming pool.

[ToraToraTora]

yes it's like what can be seen on roads and race tracks when very hot, it can actually make the road look wet as you can see what look like reflections in it.