♨ Thermal radiation
What is thermal radiation?
When you turn on the hob, you do not need to touch it to feel it heat up. Just put your hand over it and you will feel the warmth coming from it.
The warmth from the heated hob travels through the air and reaches your hand through a process called thermal radiation.
Radiation is energy that moves in space. The emitted radiation does not need materials through which to transfer its energy. It warms the space around you. The sunlight reaches the Earth in this way as well.
The heat from the hob travels through the air to reach your hand. It is radiated to you by electromagnetic radiation.
The other two ways (convection and thermal conductivity) used by the heat to travel require materials through which heat can pass.
Electromagnetic waves can transfer heat through empty space.
Sunlight passes through the empty space in each direction, heating the entire solar system. Some parts stay warmer than others. This heat that moves through the empty space is called thermal radiation.
🔍 Observe
You need a thermometer, a sheet of paper and a pen, and a desk lamp.
Ask some elderly relative to help you with this observation.
Look at the thermometer and write down how many degrees it shows on the paper.
Turn on the desk lamp. Move the end of the thermometer close to the bulb of the lamp. Hold it for a few minutes.
Check the thermometer readings again. Has the temperature changed? Why?
Because of the radiated heat. The bulb emits warmth, which heats the thermometer and increases its temperature.
