Microscopy

Question 1

What is resolution?

Answer 1

How well a microscope distinguishes between two points that are close together

Question 2

Recall the different parts of a light microscope.

Answer 2

Question 3

Out of the objective lens and the eyepiece lens, which should have the lower magnification?

Answer 3

Eyepiece lens

Question 4

Describe the purpose of each adjustment knob.

Answer 4

• Coarse adjustment knob brings sample into focus by moving the stage or the objective lenses up and down
• Fine adjustment knob controls the focus of the image

Question 5

Give the steps to view a specimen using a light microscope.

Answer 5

• Take thin slice of specimen because it needs to let light through
• Take clean slide and use pipette to put drop of water in middle of it - this secures specimen in place
• Place specimen on slide
• Add drop of stain to specimen
• Place cover slip onto specimen
• Clip slide onto the stage
• Select lowest-powered objective lens
• Use coarse adjustment knob to move stage up so slide is just underneath objective lens
• Move stage downwards until specimen nearly in focus
• Adjust focus with fine adjustment knob until you get a clear image

Question 6

What effect does adding a drop of stain to a specimen have?

Answer 6

It makes it more visible

Question 7

(Exam-style question)

Answer 7

• Use a thin section of cells
• Add a stain
• Place a cover slip on top of the sample

Question 8

(Exam-style question)

A student compares an image obtained with a light microscope with an image viewed with an electron microscope.

Suggest how the two images would differ. Explain your answer.

Answer 8

• Image viewed with electron microscope would be clearer and more detailed than image viewed with light microscope
• This is because electron microscopes have a higher resolution and a higher magnification than light microscopes

Question 9

Give two ways in which you can ensure you produce an accurate and useful drawing of a cell.

Answer 9

Any two from:

• Use a sharp pencil
• Don’t colour or shade drawing
• Label drawing with straight, uncrossing lines
• Include magnification used and a scale
• Drawing should take up at least half of space available
• Keep parts in proportion
• Draw outlines of main features