A light microscope can be used to observe microorganisms.
Observations from a light microscope can be used to identify microorganisms, including pathogens causing a disease.
The observed shape of a microorganism can help to identify it.
Use of a key and stains can help to identify a microorganism.
Growing microorganisms in specific conditions can also help to identify them.

Common misconception

Students often use the term "zoom in" instead of focus.

You must correct the term "zoom in" to focus. You are not making the image larger, you are focussing to make the image clearer.

Keywords

Microorganism - A living thing that is too small to see with the unaided eye.
Light microscope - A type of microscope that uses visible light and a system of lenses to generate magnified images of small objects.
Pathogen - A microorganism that causes disease.
Key - A series of questions about the features of an organism that help us to identify it.
Stain - A coloured liquid put onto a specimen so that the cells and their structures can be more easily seen with a light microscope.

Students could view a prepared slide under the microscope to view some bacterial cells.

Teacher tip

Content guidance

Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Video

Skip video

Worksheet

Download worksheet

Skip worksheet

Starter quiz

Download starter quiz

6 Questions

Q1.

What do we call a series of questions used to help identify organisms?

puzzle

Correct answer: key

quiz

riddle

choice

Q2.

Which part of the microscope is labelled E?

the objective lens

Correct answer: the stage

the light source

the course focus wheel

Q3.

True or false? Bacteria are multicellular prokaryotes.

true

Correct answer: false

Q4.

Which type of drug is a doctor likely to prescribe to a patient with a bacterial infection?

Correct Answer: Antibiotics, antibiotic

Q5.

Which part of the microscope would you use to bring your specimen into focus?

Correct answer: D

Q6.

Put these steps in order to explain how to make a temporary mount of onion tissue.

1 - Cut a thin slice of onion.

2 - Place the slice of onion on the glass slide.

3 - Add a drop of iodine stain.

4 - Place a cover slip over the onion.

Exit quiz

Download exit quiz

6 Questions

Q1.

Match the part of the microscope to its description.

Correct Answer:a,Eyepiece lens: viewing lens with ×10 magnification.

Eyepiece lens: viewing lens with ×10 magnification.

Correct Answer:b,Objective lenses: three lenses with different magnifications.

Objective lenses: three lenses with different magnifications.

Correct Answer:c,Stage: specimen or slide is placed here.

Stage: specimen or slide is placed here.

Correct Answer:d,Light source: illuminates the specimen so that it can be observed.

Light source: illuminates the specimen so that it can be observed.

Correct Answer:e,Coarse focus wheel: for adjusting the focus in larger increments.

Coarse focus wheel: for adjusting the focus in larger increments.

Correct Answer:f,Fine focus wheel: for adjusting the focus in smaller increments.

Fine focus wheel: for adjusting the focus in smaller increments.

Q2.

Put these steps in order to explain how a light microscope is set up.

1 - Turn the objective lenses (b) to the lens with the lowest magnification.

2 - Place the slide on the stage (c) under the clips.

3 - Turn on the light source (d).

4 - Looking from the side, turn the coarse focus wheel (e) to move the stage up.

5 - Turn the coarse focus wheel (e) to move the stage away from the lens and focus.

6 - Turn the fine focus wheel (f) to make the image as sharp and clear as possible.

Q3.

How can you increase the magnification of a light microscope?

Correct answer: increase the power of the objective lens

decrease the power of the objective lens

increase the power of the light source

move the stage closer to the lens

Q4.

What can we use to make living material easier to see under a microscope?

Correct Answer: stains, stain, Gram stain

Q5.

We can use a to identify types of bacteria.

Correct Answer: key, a key

Q6.

The image below shows bacteria growing on an agar plate containing penicillin. Penicillin works best on gram-positive bacteria. What can we conclude about the bacteria growing on the plate?

They are killed by penicillin.

Correct answer: They are not killed by penicillin.

They are most likely gram-positive bacteria.

Correct answer: They are most likely gram-negative bacteria.

Additional material

Download additional material

We're sorry, but preview is not currently available. Download to see additional material.