A surgeon uses a laser to cut through tissue during an operation. Explain why a laser beam is more suitable for this purpose than a scalpel blade, referring to the properties of laser light in your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Lasers are used in many medical procedures. Unlike a scalpel, a laser beam can be focused to an extremely small point and delivers energy directly to the tissue.
Model answer (5 marks)
Laser light is monochromatic, so all photons have the same wavelength and energy, allowing precise interaction with tissue.
Laser light is coherent; the waves are in phase, giving a stable, well‑defined beam.
The beam is highly collimated and does not spread, so it can be focused to a very small spot.
At this small spot the energy density is very high, enabling the laser to cut or vaporise tissue efficiently.
Because the laser also heats and seals blood vessels as it cuts, it reduces bleeding compared with a scalpel.
Laser light is coherent; the waves are in phase, giving a stable, well‑defined beam.
The beam is highly collimated and does not spread, so it can be focused to a very small spot.
At this small spot the energy density is very high, enabling the laser to cut or vaporise tissue efficiently.
Because the laser also heats and seals blood vessels as it cuts, it reduces bleeding compared with a scalpel.
Examiner tips
- Mention all five properties in separate sentences; keep each point concise.
- Use exam‑style terminology: monochromatic, coherent, collimated, energy density, cauterise.
- Show clear link between each property and the surgical advantage.
Common mistakes
- Confusing laser with any light source; failing to state monochromaticity.
- Omitting the cauterising effect or the reduced bleeding advantage.
Mark scheme (5 marks)
- Laser light is monochromatic (all one wavelength/frequency)
- Laser light is coherent (waves are in phase / peaks and troughs line up)
- Laser light is highly collimated / does not spread out, so it can be focused to a very small (precise) point
- The concentrated energy at the focused point is high enough to cut/vaporise tissue
- The laser cauterises (seals) blood vessels as it cuts, reducing bleeding compared to a scalpel
Related
- All Eduqas A-Level Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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