PPE Autumn Year 1 Microscopes

Question 1

Magnification

Answer 1

How much bigger the image is than the specimen

Question 2

Resolution

Answer 2

How detailed the image is
How well a microscope distinguishes between 2 points that are close together

Question 3

Magnification equation

Answer 3

Magnification= Image size/ Actual size

Question 4

Light microscope method

Answer 4

1. Clip the slide containing the specimen onto the slide
2. Select the lowest-powered objective lens
3. Use coarse adjustment knob to bring the stage up to just below the lens
4. Look through the eyepiece & use the coarse adjustment knob until the image is roughly in focus
5. Adjust focus with the fine adjustment knob until the image is clear
6. If needed swap to a higher-powered objective lens

Question 5

Eyepiece graticle

Answer 5

Fitted onto the eyepiece
Like a transparent ruler with numbers but no units

Question 6

Stage micrometre

Answer 6

A micrometre slide with an accurate scale
Used to work out the value of the divisions on the eyepiece graticule at a particular magnification

Question 7

Light microscope

Answer 7

Uses light
Low resolution
Max resolution 0.2 μm
Used to look at whole cells or tissues
Max useful magnification 1500x

Question 8

Laser scanning confocal microscope

Answer 8

Type of light microscope that uses laser beams
Scans a specimen that’s tagged with fluorescent dyes
Laser hits they dye and gives off fluorescent light
Produce a much clearer image than a normal light microscope
Look at objects at different depths in thick specimens
Multiple images- 3D images of a specimen

Question 9

Transmission electron microscope (TEM)

Answer 9

Electromagnets to focus a beam of electrons, transmitted through the specimen
Creates 2D images
Denser parts- absorb more electrons- look darker on the image
High resolution images- very small organelles & internal structures in detail
Specimens- sliced thinly
angle the specimen are cut- affect how they appear

Question 10

Scanning electron microscope
(SEM)

Answer 10

Scan a bean of electrons across the specimen
Knocks off electrons from the specimen- gathered in a cathode ray tube to form an image
Images produced- surface of the specimen
Can be 3D
Give lower resolution than TEM

Question 11

Electron micrograph

Answer 11

For an electron microscope- Treated with a solution of heavy metals
For a light microscope- staining
Metal ions act to scatter the electrons that are fired at the sample & give contrast between different structures
Images produced- always black & white (colour can be added to make images easier to interpret)

Question 12

Comparing microscopes maximum resolutions

Answer 12

Light microscope- 0.2 μm
TEM- 0.0002 μm
SEM- 0.002 μm

Question 13

Comparing microscopes maximum magnification

Answer 13

Light microscope- 1500x
TEM- can be more than 1,000,000x
SEM- usually less than 500,000x