Lecture 02- Microscopy

Question 1

Refractive index of air? Oil?

Answer 1

1, 1.4

Question 2

What is the focal point?

Answer 2

Point at which all parallel light rays will pass will pass after passing through each part of the lens. Decrease the focal point of a lens, you increase it’s diopters, or refractive power.

Question 3

What are the properties of a real image?

Answer 3

1) Outside of focal point 2) Inverted 3) can be projected onto a screen 4) Differs in size from the object. Greatest magnification = short focal length and object as close as possible to focal point.

Question 4

What are the properties of a virtual image?

Answer 4

1) Not inverted 2) Cannot be projected onto a screen 3) Can be magnified 4) No points exist at any plane in space at which rays radiating from the object are brought into focus

Question 5

What is the definition of Resolution? How do you accomplish greater resolution?

Answer 5

The ability of a microscope to distinguish two small points as separate points. Greater resolution = reducing diameter of refraction lines around the points.

Question 6

Pros/cons of Compound Optical (Light) Microscope

Answer 6

Pros: Ability to magnify, Ability to resolve structural detail
Cons: Specimen must be thin, Little contrast in unstained specimen

Question 7

Explain Phase Contrast Microscopy

Answer 7

Converts phase shifts of light that are invisible to the human eye into brightness changes that are detectable by the human eye as they travel through a transparent specimen. Useful for unstained cells and tissues and for examining live specimen.

Question 8

Explain Fluorescence Microscopy

Answer 8

Detects molecules that emit light of wavelengths within the visible range when exposed to a UV source. It is useful for detecting antigens or antibodies in staining procedures, or fluorescent tags that are injected into cells or animals.

Question 9

Explain Confocal Scanning Microscopy

Answer 9

A strongly convergent laser light produces a shallow scanning spot and a mirror system moves the laser light over a specimen. The light emerging from the spot is directed into a photomultiplier tube, analyzed, and used to recreate a 3D image on a computer.

Question 10

Explain Transmission Electron Microscopy (TEM)

Answer 10

Use a beam of electrons, rather than light, that hit a photo screen and create a highly detailed image of specimen structure.

Question 11

Which of the following components would increase resolution of a microscopic specimen?

Answer 11

Decrease Wavelength, Increase Refractive Index (n)

From the resolution equation d = (.61 x wavelength) / [n x sin(alpha)]. You want a smaller d.