Microscopy

Question 1

Refraction of light

Answer 1

Light waves transmitted through a vacuum travel at a fixed velocity
RI = Velocity of Light/(Velocity of light inside transmitting medium)

Question 2

What is the refractive index of air?

Answer 2

One. R.I. will always be more than one

Question 3

When light travels from one medium to another, it bends. What does the degree of bending depend on?

Answer 3

1. Refraction of light

2. Angle at which light strikes surface

Question 4

What is the focal point?

Answer 4

The point through which all parallel rays of light will pass after passing through each part of the lens

Question 5

What is the focal length?

Answer 5

The distance from the center of the lens to the focal point

Question 6

What are diopters?

Answer 6

Diopters measure how much a lens bends light waves (refractive power).
1 meter / focal length of a lens = the diopter

Question 7

How do you increase the # of diopters for a lens?

Answer 7

Have a stronger lens. The stronger it is, the closer the convergence(shorter focal length) which increases diopters.

Question 8

Lenses: When is a real image formed?

Answer 8

A real image is formed when the object is placed outside the focal point

Question 9

What are the characteristics of a real image?

Answer 9

• A real image is inverted

- A real image divers in size from the object

Question 10

How can you achieve greatest magnification?

Answer 10

From lenses having a very short focal length, with the object as close as possible to the focal point.

Question 11

Lenses: When is a virtual image formed?

Answer 11

When the object is placed inside the focal point

Question 12

What are the characteristics of a virtual image?

Answer 12

• Not inverted, cannot be projected onto a screen, and no points exist at any place at which rays radiating from the object are brought to a focus
• Can be magnified

Question 13

What is resolution?

Answer 13

The ability of a microscope to distinguish two small points as separate points.

Question 14

How do you improve resolution?

Answer 14

• Use higher refractive index

- Use shorter wavelengths

Question 15

What is the equation for resolution?

Answer 15

Resolution = d = (0.61λ) / n*sin(a)

Question 16

Microscopes:
Compound Optical (Light) Microscope

Answer 16

• also referred to as a bright-field microscope

Question 17

What does a condenser of a microscope do?

Answer 17

It is a lens that concentrates the light

Question 18

What does the objective less do?

Answer 18

The objective lens is usually made up of multiple lenses glued together in order to correct the focal points from a bad lens. Also fixes the halo rights that sometimes show up

Question 19

What are the pros/cons of a compound light microscope?

Answer 19

Pros
- Ability to magnify
- Ability to resolve structural detail
Cons:
- Specimen must be thin (takes a lot of work)
- Relatively little contrast in the unstained specimen (hard to see if not stained)

Question 20

Microscopes:

Phase Contrast Microscope

Answer 20

• Converts phase shifts (invisible to the ye) in light passing through a transparent specimen to brightness changes (visible to the eye) in the image
• Can be used to examine unstained cells and tissues
• Useful for examination of living cells
• No real clinical application. Mostly for lab

Question 21

Microscopes:

Fluorescence Microscope

Answer 21

• Detects molecules that emit light of wavelengths in the visible range when exposed to a UV light source
• Detects naturally occurring fluorescent molecules such as Vitamin A
• Used to detect induced fluorescence - antigens or antibodies
• fluorescent tracers injected into animals or cells

Question 22

Microscopes:

Confocal Scanning Microscope

Answer 22

• Very high resolution. Very sharp, focused points of light using a laser. Can be focused on a specimen but can only go through a small area and has to constantly be moved. But it will pick up images and sends it to a computer to focus at different levels and make a 3D image

Question 23

What are the advantages of the Confocal Scanning Microscope?

Answer 23

• very thin optical images of the specimen
• out-of-focus images are subtracted from the computer
• computer can make 3D reconstructions by stacking images

Question 24

Microscopes:

Transmission Electron Microscope

Answer 24

• Utililzes a beam of electrons rather than light
• Catode, anode,
• heated tungsten fliament (electron source)
• electromagnets - by moving magnets around, you can focus the light beams