Using a Microscope: Parts, Magnification and Slide Preparation — Answers
Answer sheet with model answers and success criteria for the Year 8 cells & classification worksheet.
Success TutoringWorksheetsAnswer sheetYear 8 · Science · Cells & ClassificationUsing a Microscope: Parts, Magnification and Slide Preparation — Answers
Part A: Parts of a microscope
Read the passage, then answer the questions.
A light microscope uses lenses to magnify small objects such as cells. Light shines up from a lamp or mirror through a thin specimen on a glass slide, then through the objective lens and the eyepiece lens to your eye.
Most school microscopes have three or four objective lenses on a turning nosepiece, often 4×, 10× and 40×. The coarse and fine focus knobs move the stage up and down to bring the image into focus.
- eyepiece lens
- objective lenses
- stage
- coarse focus knob
- fine focus knob
- diaphragm
- controls how much light passes through the specimen
- the lens you look through, usually magnifying 10 times
- lenses of different strengths just above the slide
- moves the stage a large distance to focus roughly
- the flat platform that holds the slide
- makes small adjustments to get a sharp image
Answer: eyepiece lens → the lens you look through, usually magnifying 10 times; objective lenses → lenses of different strengths just above the slide; stage → the flat platform that holds the slide; coarse focus knob → moves the stage a large distance to focus roughly; fine focus knob → makes small adjustments to get a sharp image; diaphragm → controls how much light passes through the specimen
- AIt uses less electricity.
- BIt shows the largest area, so the specimen is easiest to find and focus on.
- CIt makes cells look bigger.
- DHigh-power lenses do not work first.
Answer: It shows the largest area, so the specimen is easiest to find and focus on.
Low power has the widest field of view. Once the specimen is centred and in focus, you can switch to higher power.
Answer: True
Two hands keep the microscope steady and stop it from being dropped.
Answer: False
At high power the lens is very close to the slide. Use only the fine focus knob so the lens does not crash into and break the slide.
Part B: Magnification and cell size
Show your working.
Total magnification = eyepiece magnification × objective magnification.
The field of view is the circle of light you see. To estimate a cell's size, divide the width of the field of view by the number of cells that fit across it. Cells are usually measured in micrometres (µm): 1 mm = 1000 µm.
Answer: 40×
- 10 × 4 = 40
Answer: 400×
- 10 × 40 = 400
Answer: 10×
- 150 ÷ 15 = 10
Answer: 0.2 mm = 200 µm
- 2 ÷ 10 = 0.2 mm
- 0.2 × 1000 = 200 µm
- Agets larger and shows more cells
- Bgets smaller and shows fewer cells, but each looks bigger
- Cstays exactly the same
- Dturns upside down for the first time
Answer: gets smaller and shows fewer cells, but each looks bigger
Higher magnification shows a smaller area in more detail.
Part C: Preparing and viewing a slide
Answer: B, D, C, A, E (iodine may also be added at the edge of the coverslip after A: B, D, A, C, E is also accepted).
- Ato stop air bubbles being trapped
- Bto make the stain darker
- Cto make the onion skin thicker
- Dto warm the slide
Answer: to stop air bubbles being trapped
Lowering it at an angle pushes air out to the side, so bubbles do not block the view.
Answer: nucleus
Also accept: cell wall, cell membrane.
Answer: True
A light microscope needs light to shine through the specimen; thick samples look dark.
Model answer: They started on high power and used the coarse focus knob, so the lens was so close to the slide that it crashed into it, which can crack the slide and damage the lens. Correct method: 1. Place the slide on the stage and secure it with the clips, with the specimen over the hole. 2. Turn to the lowest-power objective (4×). 3. Looking from the side, use the coarse focus knob to bring the lens close to the slide without touching. 4. Looking through the eyepiece, turn the coarse knob slowly to move them apart until the image appears. 5. Use the fine focus knob to sharpen it and adjust the diaphragm for light. 6. Centre the part you want, switch to a higher-power objective and use only the fine focus knob.
Success criteria:
- Identifies starting on high power and using coarse focus as the errors
- Starts on lowest power
- Uses coarse focus only at low power, watching from the side
- Uses fine focus at high power
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.
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