A student prepares a slide of human cheek cells to observe under a light microscope. The student calculates the magnification of their microscope by multiplying the eyepiece lens magnification (×10) by the objective lens magnification (×40). Explain what is meant by magnification and describe how increasing the magnification of a light microscope affects what the student can see.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student uses a light microscope with an eyepiece lens of ×10 and an objective lens of ×40 to view human cheek cells. The student then switches to a higher power objective lens of ×100.
Model answer (4 marks)
Magnification is the factor by which the image of an object appears larger than the object itself.
The total magnification of a light microscope is found by multiplying the magnification of the eyepiece lens by that of the objective lens.
When the student increases the objective lens from ×40 to ×100 the image of the cheek cells will appear larger, so the cells look bigger on the screen.
However, higher magnification alone does not give a clearer image; the resolution must also improve, otherwise the image may become blurry or lose detail.
The total magnification of a light microscope is found by multiplying the magnification of the eyepiece lens by that of the objective lens.
When the student increases the objective lens from ×40 to ×100 the image of the cheek cells will appear larger, so the cells look bigger on the screen.
However, higher magnification alone does not give a clearer image; the resolution must also improve, otherwise the image may become blurry or lose detail.
Examiner tips
- Define magnification and state how total magnification is calculated. Explain the visual effect of higher magnification. Mention that resolution must also improve for a clearer image.
- common_mistakes
- :
- Confusing magnification with resolution. Saying that higher magnification always gives a clearer image. Forgetting to multiply eyepiece and objective magnifications.
Mark scheme (4 marks)
- Magnification is how many times larger the image appears compared to the actual size of the object
- Total magnification is calculated by multiplying the eyepiece lens magnification by the objective lens magnification
- Increasing magnification makes the image of the cells appear larger / the cells look bigger on the slide
- However, increasing magnification alone does not improve resolution / the image may appear blurry unless resolution also increases
Key terms in this question
magnification · eyepiece lens · objective lens
Related
- All Edexcel GCSE Biology (1BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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