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Temperature and radiation

Temperature and radiation

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Explainer Video

Tutor: Madeleine

Summary

Temperature and radiation

​​In a nutshell

All objects continuously emit and absorb infrared radiation. The amount of radiation emitted or absorbed depends on the temperature and surface of the object. 



Radiation

Definition

The emission of energy as electromagnetic waves.


Infrared radiation

All objects continuously emit and absorb infrared radiation. Objects emit radiation from their surfaces. The higher the temperature of the object, the more infrared radiation the object emits in a given time.


Depending on whether the object emits or absorbs more, the temperature of the object will change.


Changes in an object

Emits...        

Absorbs...  

Cooling down
More
Less
Heating up
Less
More
Constant temperature      
Same
Same


The surface of an object also affects the amount of radiation emitted or absorbed. A black object with a matte surface is better at absorbing and emitting radiation than a white, shiny object.


EM radiation

It's not just IR radiation that objects emit. Objects emit all types of electromagnetic radiation due to their thermal stores. 


The hotter an object is, the higher the frequency of EM radiation the object emits. 


Curiosity: A metal at room temperature will emit infrared radiation. As it heats up the frequency of EM radiation emitted will increase. This goes from infrared to visible light frequencies - starting at the red frequencies of light. This is why metals glow when they are heated.
​

​

The Earth's temperature 

The temperature of the Earth depends on the amount of radiation it absorbs and emits. 


  • During the day, radiation is absorbed from the Sun which causes in increase in local temperature.

  • At night, less radiation is absorbed than emitted which causes a decrease in local temperature.


Changes to the Earth's atmosphere can affect its temperature. If the atmosphere absorbs more radiation than it emits, the overall temperature of the Earth will increase. This is known as global warming.


The changes to the Earth's atmosphere are caused by greenhouse gases. These gas molecules absorb more of the radiation that is emitted by the Earth's surface. This stops it from being emitted and means the atmosphere is absorbing more radiation than it emits.


Read more

Learn with Basics

Learn the basics with theory units and practise what you learned with exercise sets!
Length:
Conductors and insulators of heat

Unit 1

Conductors and insulators of heat

Energy transfer by heating

Unit 2

Energy transfer by heating

Jump Ahead

Score 80% to jump directly to the final unit.

Optional

Temperature and radiation

Unit 3

Temperature and radiation

Final Test

Test reviewing all units to claim a reward planet.

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FAQs - Frequently Asked Questions

What is the relationship between climate change and radiation?

Changes to the Earth's atmosphere can affect its temperature. If the atmosphere absorbs more radiation than it emits, the overall temperature of the Earth will increase. This is known as global warming.

Is temperature affected by radiation?

As an object cools down, it emits more IR radiation than it absorbs. As an object warms up, it absorbs more IR radiation than it emits. Objects that stay the same temperature, emit as much IR radiation as they absorb.

Does higher temperature mean more radiation?

The higher the temperature of the object, the more infrared radiation the object emits in a given time. All objects continuously emit and absorb infrared radiation. Objects emit radiation from their surfaces.

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