Microscopes

Question 1

Define magnification

Answer 1

Magnification is how much bigger a sample appears to be under the microscope than it is in real life

Question 2

Define resolution

Answer 2

The minimum distance apart that 2 objects can be in order for them to appear as separate items (the absolute to distinguish between two points on an image)

Question 3

Describe a light microscope

Answer 3

• uses a beam of light focused by a glass lenses
• light has a longer wavelength than electrons so light microscope has lower resolution than electron microscopes
• light penetrates sample
• specimen needs to be thin (1 cell)
• 2D image
• Image seen in colour due to stain
• living specimen can be viewed

Question 4

Describe a TEM microscope.

Answer 4

• uses a beam of electrons focused by electromagnets
• elections have a shorter wavelength than light so TEM has higher resolution than light microscope
• electrons penetrate sample
• specimen needs to be extremely thin
• 2D image
• Image seen in black and white
• in a vacuum so can’t view live specimen

Question 5

Describe a SEM microscope

Answer 5

• uses a beam of electrons focused by electromagnets
• electrons have shorter wavelength than light so SEM has higher resolution than light microscope
• electrons bounce off the surface of the sample
• 3D image
• image seen in black and white
• in a vacuum so no live specimens

Question 6

How do you prepare a slide for a microscope? (Light microscope)

Answer 6

• thin, often 1 cell thick so light can pass through
• stained so you can distinguish between different components
• sample is placed on slide with a drop of water so the sample doesn’t dry out
• cover slip on top, lowered with a mounted needle to prevent bubbles