Microscopes

Question 1

What are the features of a light microscope?

Answer 1

The radiation used is light, the source of radiation is a light bulb, the lenses are glass. The wavelength radiation is 400-600nm, the maximum magnification is x1500 and the limit of resolution is 0.2 micrometers. It is cheap and small and portable. Samples must be thin and stained and air is needed, it can only show thin sections of living things.

Question 2

What are the features of an electron microscope?

Answer 2

The radiation used is electrons, the source of radiation is from an electron gun and the lenses of electromagnets. The wavelength of radiation is 10-100nm, the maximum magnification is x500000 and the limit is resolution is 0.1nm for TEM and 20nm for SEM. It is very expensive and very large and not portable. A vacuum is needed and it can only show dead things but shows them very detailed and in 3D.

Question 3

Advantages of electron microscopes?

Answer 3

The resolution is 0.1nm, has high magnification of x500000, it gives detailed images of organelles and gives a 3D image so shows contours.

Question 4

Disadvantages of electron microscopes?

Answer 4

Electron beams are deflected by air molecules, very large and expensive. Training and skill is needed.

Question 5

Features of the Transmission Electron Microscope (TEM)?

Answer 5

The image may include artefacts due to preparation. It’s the most common and the highest resolution is 0.1nm. Thin sections are needed for electrons to pass though to get the image. They pass a beam of electrons through a specimen, they are detected on a fluorescent screen showing an image.

Question 6

Features of a Scanning Electron Microscope (SEM)?

Answer 6

Reflected beams are focused on a fluorescent screen to make image. Resolution is only 20nm. Thicker structures can be used as electrons only bounce off to make the 3D image. They pass a beam of electrons over a surface of specimen in the form of a scanning beam.

Question 7

Advantages of light microscopes?

Answer 7

They are cheap and portable and show images of living things.

Question 8

Disadvantages of light microscopes?

Answer 8

Samples must be thin sections and stained. It also has a much lower magnification of x1500 and a resolution of 0.2 micrometers.

Question 9

Define magnification?

Answer 9

The number of times larger an image is compared to the real size of the object.

Question 10

Define resolution?

Answer 10

The ability to distinguish between two separate points.

Question 11

1cm =

Answer 11

10mm

Question 12

1mm =

Answer 12

1000 micrometers.

Question 13

1 micrometers =

Answer 13

1000nm (nanometres)

Question 14

How to work out magnification?

Answer 14

A M

I = image size
A = actual size
M = magnification

Question 15

What structures can’t be seen under a microscope?

Answer 15

Mitochondrion
Ribosome
Endoplasmic Reticulum
Cell Surface Membrane