# A metal bar is heated in a furnace. As the temperature of the bar increases, the colour of the light it emits changes from dull red, to orange, to yellow, and eventually to white. Explain what these observations tell us about the relationship between temperature and the radiation emitted by the bar.

> Eduqas GCSE Physics — 6.5 Black body radiation · Explain · 4 marks

> A metal bar is placed inside a furnace and heated to very high temperatures. At first the bar glows dull red, then orange, then yellow, and finally white-hot.

## Mark scheme (4 marks)

1. All objects emit electromagnetic radiation / the bar emits radiation because it is hot
2. As temperature increases, the peak wavelength of emitted radiation decreases / the radiation shifts towards shorter wavelengths
3. At higher temperatures the bar emits more radiation / greater intensity / more energy per second
4. White light contains all visible wavelengths / the bar appearing white shows it emits across the whole visible spectrum, consistent with a very high temperature

## Key terms

- [temperature](https://www.gradenine.co.uk/glossary/temperature)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-metal-bar-is-heated-in-2e7936a6) · Published by Druglandscape Ltd.