# A laser is used in a supermarket barcode scanner to read the barcodes on products. Explain why laser light is well suited to this application, referring to the properties of laser light in your answer.

> WJEC A-Level Physics (Wales) — 2.8 Lasers · Explain · 5 marks

> Barcode scanners in supermarkets work by shining light onto a barcode and detecting the pattern of reflected light. The scanner must read the barcode accurately from a short distance away.

## Mark scheme (5 marks)

1. Laser light is monochromatic (single wavelength / single colour / single frequency)
2. Laser light is coherent (waves are in phase with each other)
3. Laser light is collimated / forms a narrow, parallel beam that does not spread out
4. The narrow beam allows it to be aimed precisely at the small bars of the barcode
5. The consistent / single wavelength means the detector can reliably distinguish reflected light from background light, giving a clear signal

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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