# Describe the properties of laser light that make it suitable for use in eye surgery, and explain why ordinary white light from a lamp would not be suitable for the same purpose.

> Eduqas A-Level Physics — 2.8 Lasers · Describe and Explain · 5 marks

> Lasers are used in medicine to carry out delicate surgical procedures, including operations on the human eye. The surgeon can direct the laser beam with great precision to a specific point on the eye.

## Mark scheme (5 marks)

1. Laser light is monochromatic (all one wavelength/colour)
2. Laser light is coherent (all waves in phase / same frequency and phase)
3. Laser light is collimated / forms a very narrow, parallel beam that does not spread out
4. These properties allow the laser beam to be focused onto a very precise, small spot on the eye (high precision / energy delivered to exact location)
5. Ordinary white light is not monochromatic / not coherent / spreads out in all directions, so it cannot be focused precisely enough / would damage surrounding tissue

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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