# 15 Thermal Radiation Example: Detailed Explanations

This article discusses about thermal radiation example. Radiation is nothing but a mode of heat transfer which does not need any medium for the transfer to take place.

It is notable fact that for radiation heat transfer to take place, even physical contact is not required. The heat gets transferred without any medium in between or physical contact between the two systems. We shall discuss more about different examples of radiation heat transfer.

## What is heat transfer?

Heat transfer is the process in which thermal energy and entropy is transferred from one system to another.

Major factor which affects the heat transfer is the temperature difference between the two systems. The heat will flow always in the direction from high temperature to low temperature system. Although there are multiple modes of heat transfer but we shall limit our discussion to only radiation heat transfer.

Image credits: Kmecfiunit, cmglee, Heat-transmittance-means2CC BY-SA 4.0

## What is radiation heat transfer?

In simple words, radiation heat transfer is the type of heat transfer in which the system at lower temperature absorbs, reflects or transmits the heat that is being emitted by system at higher temperature.

It is a notable fact that radiation heat transfer does not need any medium or physical contact. The best example of radiation heat transfer is Earth getting heated by the heat being emitted by sun. This transfer of heat takes place through radiation heat transfer. We shall study more examples of radiation heat transfer in the later sections of this article.

## Example of radiation heat transfer

Radiation heat transfer takes place around us but we usually ignore it. If we look around, there are many examples where we can see radiation heat transfer taking place.

Let us see some common examples of radiation heat transfer. They are given below-

## Heat transfer taking place inside microwave oven

Microwave oven is used to heat food. The microwave oven sends out electromagnetic waves which penetrate the food and makes it warm. This way the heat transfer takes place.

## Earth getting heated by Sun

Sun sends out electromagnetic waves to the vacuum of space. These waves are collected by Earth as a result of which the planet gets heated up. This is the most common example of heat transfer done by radiation.

## Heat being emitted by a radiator

A radiator in vehicle sends out heat to the surroundings. If we are standing near the radiator, we are bale to feel the heat due to radiation.

## Light being emitted by an incandescent lamp

An incandescent lamp becomes hot after being lit for some while. This heat is transferred to the surroundings with the help of radiation heat transfer. If we are standing near this lamp, we will be able to feel the heat. This is due to Radiation heat transfer.

## Gamma ray emission from a nucleus

Gamma rays are an example of electromagnetic waves. These waves don’t need any medium to travel hence we can say that these waves travel with the help of radiation. When gamma rays are emitted by nucleus, they travel with the help of radiation. Any object coming in its close vicinity may experience radiation effects.

## Feeling warm when standing beside a car whose engine is hot

When a car is used for long period, the engine becomes hot due to its long operation duration. The engine surface is hot but we can feel the heat without even touching the engine itself. This happens as a result of radiation heat transfer from the surface of engine to its surroundings.

## Heat coming out of hot food

We feel the heat from warm food without even touching it. The plate becomes hot due to conduction taking place. But when we feel the heat without touching the plate or food, it is because of radiation heat transfer.

## Metal rod when heated emits heat to surroundings

When we heat a metal rod using an external heat source, the rod gets heated up by the process of conduction. This heated rod transfers the heat to surroundings using radiation heat transfer. We need not touch the rod in order to feel the heat, we can just put our hand near the rod and we will know the rod is warm or not.

## Molten metal used in casting emits heat in the surroundings

For casting a product, metal is melted into liquid. This requires immense heat, this heat is then emitted back to the surroundings. This happens as a result of radiation heat transfer between molten metal and surroundings.

## Magma emits heat to its surrounding areas

Similar to molten metals, magma is molten rock. These molten rocks emit heat to the surroundings with the help of radiation heat transfer.

## Standing beside a fire makes us feel warm

Fire emits heat to the surroundings. Without touching fire also, one can get burns on his hands. We can say that fire emits heat by the process of radiation heat transfer.

## Bike’s silencer emits heat when the bike is being driven or has just been driven

The silencer used in bikes become hot after a long ride. The silencer is so hot that our legs can feel the heat just by keeping them near the silencer. If we touch the silencer we are surely going to get burnt due to heat transfer by conduction. But when we feel hot without touching it, it is due to radiation heat transfer.

## We feel warm when standing beside a stove

When we lit up a stove, the heat from the stove s transferred to the surroundings with the help of radiation heat transfer.

## Laptop’s body emits heat when it is used for long hours

The electronics used in laptop get hot when the laptop is used for long hours. This heat is transferred to the surroundings with the help of radiation heat transfer.

## Hot metal emits heat after being machined

A metal becomes hot after it gets machined. This heat is generated due to friction. This generated heat is emitted back to surroundings with the help of radiation heat transfer.

Abhishek

I, Abhishek Khambhata, have pursued Btech in Mechanical Engineering. Throughout four years of my engineering, I have designed and flown unmanned aerial vehicles. My forte is fluid mechanics and thermal engineering. My fourth year project was based on performance enhancement of unmanned aerial vehicles using solar technology. I would like to connect with like minded people.