Biology

Question 1

Light and Electron Microscope

Answer 1

• Compound light microscope magnifies up to 1000x magnification.
• Binocular/ Stereo dissecting microscopes magnifies 10x to 90x magnification.
• Transmission electron microscope.
• Scanning electron microscope.

Question 2

Electron Microscope

Answer 2

They are large, expensive and not portable.

Question 3

Electron microscopes

Answer 3

Transmission electron images appear flat (two dimensional) and are in black and white, unless a colour is added by computer. This picture is of a mitochondrion and includes a scale bar.
Scanning electron microscope images are 3- dimensional. They are also sometimes at a lower magnification than transmission electron microscope images.

Question 4

Characteristics of Light and electron Microscopes

Answer 4

Characteristic Light microscope Electron microscope

Illumination Light Electrons
Focussed by Glass lenses Electromagnets
Maximum magnification X1500 X50 million
Resolving power 200 nm (0.2 µm) 78 picometres
78 x 10-12m
Specimens Living or dead Dead (vacuum)
Specimen preparation Relatively cheap Relatively expensive
Images in colour Yes No (colour added by computer)

Magnification and resolving power

Magnification is how much larger something is.
Resolving power is the ability to distinguish/separate two objects that are close together.
Resolving power = half the wavelength of the light or electrons.

Question 5

Light microscopes

Answer 5

Cheek cells, also known as squamous epithelial cells are used as an example of a generalised animal cell. This image shows bacteria so you get an idea of the size difference.