Why is cooking a burger on a BBQ caused by radiation?
When a grill is heated, the heat energy is transferred between the grill and the hamburger patty. This type of energy is known as thermal energy.
As the grill becomes hot, its molecules vibrate rapidly and bounce off each other. Heat is then produced and is transferred to the meat, thereby cooking it. As heat from the glowing coals strikes the food, infrared radiation--(a type of electromagnetic energy) will travel in any direction and will heat and cook the food.
Infrared radiation is part of the electromagnetic spectrum and lies next to the color red, which is in the visible light range of the spectrum. Infrared radiation is invisible to the human eye. These waves carry energy that can be used to cook food. When infrared radiation strikes the outer molecules of the food, they become agitated, causing some heat to be generated which then passes to the middle of the food and helps to cook it.
I have included a diagram showing the electromagnetic spectrum and its various wavelengths.