---
title: "Infrared Emission, Absorption and the Temperature of a Body"
description: "Every object emits infrared, and how much it emits rises steeply with its temperature and depends on its surface. A body settles at the temperature where what it emits matches what it absorbs, which i"
canonical: https://lightmysky.com/learn/science/infrared-emission-absorption-and-the-temperature-of-a-body-mt_xwh9uZ8gCl
source: https://lightmysky.com/learn/science/infrared-emission-absorption-and-the-temperature-of-a-body-mt_xwh9uZ8gCl.md
retrieved: 2026-09-12
---

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# Infrared Emission, Absorption and the Temperature of a Body

Every object emits infrared, and how much it emits rises steeply with its temperature and depends on its surface. A body settles at the temperature where what it emits matches what it absorbs, which is why a matt black surface heats and cools fastest and why the Earth has the average temperature it does.

Subject: Science · Area: Waves, Light & Sound · Ages 15 to 16
Page: https://lightmysky.com/learn/science/infrared-emission-absorption-and-the-temperature-of-a-body-mt_xwh9uZ8gCl

## Ready when they can

- Predicts which of two surfaces will heat faster in sunlight and which will cool faster in the dark, and gives the same reason for both
- Explains the steady temperature of an object as the point where emission and absorption balance
- Applies the balance to the Earth and says what changes when the atmosphere absorbs more of the outgoing infrared

## Lesson: Why dark cans cool fastest

Every object glows with infrared set by its temperature: hotter means much more emission. Dark matt surfaces are the champions at both emitting and absorbing, while shiny light surfaces lag at both. That single symmetry runs daily life.

**Example.** Fill one matt black can and one shiny white can with warm water and leave both out at night. The black can cools faster. Put them in morning sun and the black one heats faster too. The same property explains both: what absorbs well also emits well.

A body settles at the temperature where what it emits matches what it absorbs. The Earth works the same way: sunlight arrives mostly visible, and the Earth sends energy back out as infrared. When the atmosphere absorbs a bigger share of the outgoing infrared, the surface warms until its rising emission closes the gap.

**Tip.** Sort every heat puzzle into three methods first. A warming spoon is conduction through touch, a rising plume is convection by moving fluid, and sun on skin is radiation needing no medium. The infrared story is pure radiation: surfaces trade invisible light until their books balance.

**Recap.** Dark matt wins at both giving and taking infrared, and every body rests where emission matches absorption.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Specific Heat Capacity as a Material Property](https://lightmysky.com/learn/science/specific-heat-capacity-as-a-material-property-mt_mXC9IKom3P)
- [The Electromagnetic Spectrum: Uses and Dangers](https://lightmysky.com/learn/science/the-electromagnetic-spectrum-uses-and-dangers-mt_P_NXNSo1zQ)
- [Conduction, convection, and radiation](https://lightmysky.com/learn/science/conduction-convection-and-radiation-mt_ySnOkVIu22)

## Opens up

- [Blackbody Radiation and the Quantum of Energy](https://lightmysky.com/learn/science/blackbody-radiation-and-the-quantum-of-energy-mt_B2Bk2IAOa9)
- [Earth's Energy Balance and the Greenhouse Effect, Quantified](https://lightmysky.com/learn/science/earths-energy-balance-and-the-greenhouse-effect-quantified-mt_dDV2fr06nO)