Topic 2.1.1 - Observing cells

Question 1

How does a light microscope work?

Answer 1

Light beam is reflected by a mirror through a specimen
Beam passes through lens which magnifies the image

Question 2

How does a scanning electron microscope work?

Answer 2

Emits an electron beam
Electrons bounce off the surface of the specimen and are received on
a senor

Question 3

How does a Transmission electron microscope work?

Answer 3

Emits an electron beam where electrons pass through specimen.
Harder for electrons to pass through thicker parts of the specimen which contract the 2D image produced.
Electrons have a smaller wavelength than light so a better resolution

Question 4

Advantages and disadvantages of a light microscope

Answer 4

Advantages - Relatively cheap and available, light and portable
Can see parts of living plants and animals
Disadvantages - Limited resolution and magnification

Question 5

Advantages and disadvantages of an electron microscope

Answer 5

Advantages - Large amounts of magnification and resolution
Disadvantages - All specimens are examined in a vacuum as air would scatter electrons.
Very expensive
Have to be kept at a constant pressure and temperature

Question 6

Why is the resolution of an electron microscope better than a light microscope?

Answer 6

Electrons have a smaller wavelength than light.

Question 7

Describe the method of using a graticule.

Answer 7

Place a stage micrometer on the stage of the microscope
Line up the divisions on the eyepeice graticule with a fixed point on the stage micrometer
Count number of divisions on the eyepeice graticule that correspond with a set measurement on stage micrometer
Calculate the distance of one division on the eyepeice graticule