Microscopy

Question 1

What are the two types of electron microscopes?

Answer 1

Transmission electron microscope & scanning electron microscope

Question 2

What is magnification?

Answer 2

How many times larger the image is compared to the object

Question 3

What is resolution?

Answer 3

Minimum distance between two objects where they can still be viewed as seperate.

Question 4

What is the resolution determined by in optical (light) microscopes and electron microscopes?

Answer 4

Optical (light) microscope: wavelength of light

Electron microscope: Wavelength of the beam of electrons

Question 5

Describe the optical (light) microscope

Answer 5

• a beam of light is condensed to create the image
• poorer resolution due to light having a longer wavelength
• lower magnification
• colour images
• can view living samples

Question 6

Describe the electron microscope (scanning & transmission)

Answer 6

• a beam of electrons is condensed to create the image
• higher resolution due to electrons having a short wavelength
• higher magnification
• sample must be in vacuum, therefore cannot view living samples

Question 7

Describe the transmission electron microscope (TEM)

Answer 7

The specimen is cut and therefore is extremely thin and also stained and placed in a vacuum. The electron gun produces a beam of electrons that passes through the specimen. Denser parts absorb more electrons and therefore appear darker. Image is 2D and shows detailed internal structures.

Question 8

Describe the scanning electron microscope (SEM)

Answer 8

Specimen does not have to be thin. The electrons are beamed onto the surface and are scattered in different ways depending on the contours. This produces a 3D image.

Question 9

What is the formula for magnification?

Answer 9

Magnification = Image size/Actual size

Question 10

Write the conversions for magnification.

Answer 10

metres, millimetres, micrometres, nanometres (x1000)