There are three ways in which heat is transmitted:
1. By Conduction, when the transmission is by the direct contact.
2.By Convection, heat transfer in fluids (like water or the air, for example).
3.By Radiation, by the electromagnetic waves (they can travel through any medium and in vacumm)
According to this, the examples that apply for radiation are:
Earth is heated by energy from the Sun.
Because in space there is no medium, there is vacuum, and the only way to transmit heat is by radiation (Electromagnetic waves don’t need a medium to be transported)
Soup is heated in a microwave.
Because microwave ovens use electromagnetic waves to heat the water particles in the food.
The other examples apply for:
Conduction:
Troy’s hand is burned when he touches hot wax. (Direct contact between Troy’s hand and the hot wax)
Convection:
Water is boiled in a pot on a stove burner. (Here the medium is water)
A hot dog is held over a fire and gets warm. (Here the medium is air)
