Continuous & Line Spectra (SQA National 5 Physics): Revision Note

Continuous & line spectra

Continuous spectra

• White light contains all the wavelengths and frequencies of the electromagnetic spectrum

• When white light is split up by a prism, all the colours in the visible range can be observed

• This is called a continuous spectrum

Continuous spectrum of light

A continuous spectrum is one which shows all wavelengths of light

Line spectra

• When white light passes through a gas, certain wavelengths of light are found to be missing from the spectrum

• This is because atoms in a gas absorb light at specific wavelengths

• The specific wavelengths depend on the elements present in the gas

• This produces a continuous spectrum with dark lines at the wavelengths where light is absorbed

• This is called an absorption spectrum

Absorption spectrum of light

An absorption spectrum is one which shows all wavelengths of light with dark lines where specific wavelengths have been absorbed

• Every element produces a unique pattern of spectral lines

• Therefore, absorption spectra can be used to identify which elements are present in a gas