How do you find actual size from a drawing?

actual size = image size ÷ magnification.

How do you work out total magnification?

Multiply the eyepiece magnification by the objective magnification.

Why start with the lowest-power objective lens?

It gives the widest field of view, and the lens is far from the slide so it is less likely to crack it.

What does the coarse focus knob do?

It moves the lens or stage a large distance to bring the specimen roughly into focus.

Why must tissue on a slide be thin?

So that light can pass through it.

Why add a stain to a slide?

It colours structures so they are easier to see.

What are three rules for a scientific drawing?

Sharp pencil lines, no shading, and labels with ruled lines that do not cross. Include a title and scale.

Using a microscope and magnificationIB MYP Sciences: Flashcards

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What is the formula for magnification?

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What is the formula for magnification?: magnification = image size ÷ actual size.
How do you find actual size from a drawing?: actual size = image size ÷ magnification.
How many micrometres are in 1 mm?: 1000 µm.
How do you convert mm to µm?: Multiply by 1000.
How do you work out total magnification?: Multiply the eyepiece magnification by the objective magnification.
Why start with the lowest-power objective lens?: It gives the widest field of view, and the lens is far from the slide so it is less likely to crack it.
What does the coarse focus knob do?: It moves the lens or stage a large distance to bring the specimen roughly into focus.
What does the fine focus knob do?: It makes the image sharp.
Why must tissue on a slide be thin?: So that light can pass through it.
Why lower a cover slip at an angle?: To avoid trapping air bubbles.
Why add a stain to a slide?: It colours structures so they are easier to see.
What are three rules for a scientific drawing?: Sharp pencil lines, no shading, and labels with ruled lines that do not cross. Include a title and scale.

Exam questions on Using a microscope and magnification

A student in Mumbai is using a light microscope for the first time to look at a prepared slide of onion cells. The microscope has an eyepiece lens of magnification ×10, three objective lenses (×4, ×10 and ×40), a stage, a coarse focus knob and a fine focus knob.
Explain why the student should start by looking at the slide with the lowest-power objective lens.2 marks
A technician in Cape Town prepares a temporary slide of the thin, transparent skin from the inside of an onion bulb. She has forceps, a dropper of water, iodine solution, a microscope slide and a cover slip.
Describe how the cover slip should be placed on the specimen, and give the reason for this.2 marks
A student in Seoul observes cheek cells under a light microscope and makes labelled drawings. Her teacher asks her to calculate the magnification of each drawing so that other students can work out the real size of the cells.
One cheek cell in her drawing is 60 mm wide. Its actual width is 0.03 mm. Calculate the magnification of the drawing.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).