S1 Science: Microscope Skills And Cell Observation (Paper 2: Intermediate)

S1 Science: Microscope Skills and Cell Observation (Paper 2: intermediate)

2026-11-12

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S1 Science: Microscope Skills and Cell Observation (Paper 2: intermediate)

This paper turns the same formula around: from real size in micrometres to image size in millimetres, from an old field diameter to a new one, and from cell counts back to an area ratio. Units and squares are the whole point.

Direct answers　Write 1 mm = 1 000 micrometres above each question before substituting; that alone halves the mistakes.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S1 Science: Microscope Skills and Cell Observation
Level	S1 Science

02　Questions (10 items)

FoundationWhy should you start with low power and then move to high power?
FoundationHow should a cover slip be lowered so that no air bubbles form?
FoundationWhich stain is commonly used for cheek cells and what does it do?
IntermediateA cell is 50 micrometres across. At 400x, what is the diameter of its image in millimetres?
IntermediateTotal magnification changes from 100x to 400x. What fraction of the original area does the field now cover?
IntermediateAt 100x a cell image measures 8 mm. What is the real diameter in micrometres?
ChallengeAt 100x the field diameter is 1.8 mm. What is it at 400x?
ChallengeAt 400x a cell image measures 12 mm long. What is the real length in micrometres?
ChallengeAbout 240 evenly spread cells fill the field at 100x. At 400x, how many are visible at the same density?
Error redoWhat is wrong with using the coarse focus knob at high power?

03　Answers and one-line notes

#	Answer	One-line note
1	Low power gives a wide field, so the specimen is easy to find; only then switch to high power for detail.	Starting at high power means a tiny field and a long search before anything is found.
2	Let one edge touch the water at about 45 degrees, then lower the other edge slowly.	Tilting pushes the air ahead of the glass; dropping it flat traps air in the middle.
3	Methylene blue, which dyes the nucleus dark blue so the cell outline and nucleus are easy to see.	Methylene blue is a basic stain; animal cells have no wall, so staining makes the outline visible.
4	20 mm	50 micrometres = 0.05 mm and 0.05 x 400 = 20 mm.
5	One sixteenth	The diameter shrinks to one quarter and area goes with the square of the diameter, giving one sixteenth.
6	80 micrometres	8 / 100 = 0.08 mm and 0.08 x 1 000 = 80 micrometres.
7	0.45 mm	Magnification rises four times, so divide the diameter by four: 1.8 / 4 = 0.45 mm.
8	30 micrometres	12 / 400 = 0.03 mm and 0.03 x 1 000 = 30 micrometres.
9	15 cells	The area becomes one sixteenth, so 240 / 16 = 15 cells.
10	The high power lens sits very close to the slide, so the coarse knob can crack the slide or damage the lens; use the fine knob.	Find the image at low power with the coarse knob, then use only the fine knob once high power is in place.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Convert units before calculating: turn micrometres into millimetres or the other way round, otherwise answers shift by a factor of a thousand. A smaller field shrinks by the magnification factor, not by the magnification number itself in area terms.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.