A surgeon uses a laser to perform a delicate eye operation. Explain why laser light is more suitable than ordinary white light from a lamp for this medical procedure.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Lasers are used in medicine for many precise surgical procedures, including correcting problems with vision.
Model answer (5 marks)
Laser light is monochromatic, so the energy is delivered at a single wavelength, allowing precise control of the interaction with tissue.
Laser light is coherent; all waves are in phase, giving a stable, high‑intensity beam.
It is emitted as a very narrow, parallel beam (highly collimated) that does not spread.
This narrow beam can be focused on a very small area of the eye, minimising damage to surrounding tissue.
Ordinary white light from a lamp spreads in all directions and contains many wavelengths, making it impossible to direct precisely enough for surgery.
Laser light is coherent; all waves are in phase, giving a stable, high‑intensity beam.
It is emitted as a very narrow, parallel beam (highly collimated) that does not spread.
This narrow beam can be focused on a very small area of the eye, minimising damage to surrounding tissue.
Ordinary white light from a lamp spreads in all directions and contains many wavelengths, making it impossible to direct precisely enough for surgery.
Examiner tips
- Mention monochromaticity, coherence, collimation and precise targeting; link each to surgical advantage.
- Use the exact wording from the mark scheme to secure full marks.
Common mistakes
- Confusing laser light with any light source; failing to note the single wavelength. Over‑emphasising intensity without mentioning beam collimation. Using vague terms like "bright" instead of "monochromatic" or "coherent".
Mark scheme (5 marks)
- Laser light is monochromatic (one wavelength/colour) so the energy delivered to the tissue is precisely controlled
- Laser light is coherent, meaning all waves are in phase with each other
- Laser light is emitted as a very narrow, parallel beam (highly collimated) that does not spread out
- The narrow beam means energy can be directed at a very small, precise area of the eye without affecting surrounding tissue
- Ordinary white light from a lamp spreads out in all directions and contains many wavelengths, making it impossible to direct precisely enough for surgery
Key terms in this question
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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