Emission and Absorption Spectra

This lesson covers emission and absorption spectra as required by the Edexcel GCSE Physics specification (1PH0), Topic 5: Light and the Electromagnetic Spectrum. You need to understand how hot and cool gases produce different types of spectra, why each element has a unique spectrum, and how spectra are used to identify elements — including in stars.

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Types of Spectra

There are three main types of spectra that you need to know:

1. Continuous Spectrum

A continuous spectrum contains all wavelengths (all colours) with no gaps. It appears as a smooth rainbow of colours from red to violet.

• Produced by hot solid objects (e.g. a filament lamp, the Sun's surface).
• Also produced by hot liquids and very dense hot gases.
• The colours blend smoothly into one another with no dark lines or bright lines.

2. Emission Line Spectrum

An emission line spectrum consists of bright coloured lines on a dark (black) background. Each line corresponds to a specific wavelength of light.