2.1 Cell Strucutre

Question 1

What is magnification

Answer 1

Is the number of times larger an image appears, compared with the size of the object originally

Question 2

What is resolution?

Answer 2

The ability of an optical instrument to see or produce an image that shows fine detail clearly

Question 3

Why are optical microscopes good to use?

Answer 3

They are relatively cheap
They are easy to use
They are portable so can be used in the field as well as classroom
They can be used to view whole living specimens

Question 4

What is the maximum magnification and resolution of a optical microscope?

Answer 4

X1500 or X2000

0.2 micrometers or 200 nm

Question 5

How does a optical microscope work?

Answer 5

1. The specimen on a slide is clipped onto the stage
2. The objective lens then needs to be placed on the lowest power
3. Adjust the coarse focus knob until the image is in view and relatively clear
4. Use the fine focus knob to improve the resolution of the image

Question 6

How do you calculate total magnification?

Answer 6

Total magnification = magnifying power of the objective lens x magnifying power of the eyepiece lens

Question 7

What is a photomicrograph?

Answer 7

Photograph of an image seen using an optical microscope

Question 8

What are laser scanning microscopes also called?

Answer 8

Confocal microscopes

Question 9

How do laser microscopes work?

Answer 9

They use laser light to scan an object point by point and assemble, by computer, the pixel information into one image, displayed on a computer screen.

Question 10

What do images of a laser microscope show?

Answer 10

They show high resolution and show high contrast.

Question 11

What can laser microscopes also do and what are they used for?

Answer 11

They can also focus on structures at different depths due to having depth sensitivity. Whole living specimens can viewed as well as cells.
They are used in the medical profession, to observe fungal filaments in the cornea of the eye.

Question 12

What is an electron microscope?

Answer 12

A microscope that uses a beam of fast travelling electrons.

Question 13

What does this mean for the resolution of images from an electron microscope?

Answer 13

They have much higher resolution and can give clear and highly magnified images.
The electrons are travelling with a wavelength of 0.004nm ( tiny)

Question 14

How does an electron microscope work?

Answer 14

Electrons are fired from a cathode at a wavelength of 0.004 nm and focused, by magnets rather than glass lens, on a screen or photographic late

Question 15

Why does an electron microscope have a much better resolution than a optical microscope?

Answer 15

Because the fast travelling electrons have a wavelength about 125,000 times smaller than that of the central part of the visable light spectrum.