Lecture 2 Learning Objectives

Question 1

Janssens contribution to microscopy

Answer 1

Produced first compound microscope

Question 2

Hooke’s contribution to Microscopy

Answer 2

Described cork and introduced the term cell

Question 3

Leeuwenhoek’s contribution to microscopy

Answer 3

Made over 200 simple microscopes capable of 100x magnification
Observed RBCs, Protozoa, skeletal muscle, sperm, bacteria

Question 4

Define refraction

Answer 4

Light is refracted when the velocity and angle are changed as it passes through different mediums

Question 5

Calculate refractive index

Answer 5

RI = speed of light / speed of light through the medium

Question 6

Focal point

Answer 6

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

Question 7

Focal length

Answer 7

Distance from the center of the lens to the focal point

Question 8

How does focal point and focal length relate to refraction?

Answer 8

As light passes through a lens, light is refracted and focused some distance from the lens at the focal point

Question 9

Formation and characteristics of a real image

Answer 9

Real- side where the light actually goes after interacting with the lens. Opposite side of the lens is the light source.
Inverted. Can be projected

Question 10

Virtual image formation and characteristics

Answer 10

On the same side of the lens as the light source.
Not. Inverted.
Cannot be projected, can be magnified

Question 11

Resolution

Answer 11

The ability of a microscope to distinguish two small points as separate
D = 0.61 lambda / N sinA.

Question 12

How can we increase resolution?

Answer 12

Decreasing wavelength

Increasing refractive index

Question 13

Components of compound light microscope

Pros and Cons

Answer 13

Light source, condenser, stage, objective lens, ocular lens
Pro: can magnify and resolve structural detail
Con: specimen must be thin, relatively little contrast in unstained specimen

Question 14

Explain how a phase contrast microscope works and list its advantages

Answer 14

Converts phase shifts of light to brightness changes in the image
Pro- can use to examine unstained and living cells and tissues

Question 15

Explain how confocal scanning microscopy works and list its advantages

Answer 15

Adds resolution and contrast by adding a pinhole to eliminate out of focus light, uses raster (pixel) system to scan each section and recreate a 3D Image
Pro: very thin optical images are a created. Out of focus images are removed by computer. 3D images possible

Question 16

Describe how TEM works and list its advantages and disadvantages

Answer 16

Uses a beam of electrons instead of light. Uses cathode, electron sourced, anode and a series of electromagnets to hurl electrons at an image.
Pros- extremely high resolution
Cons- Cannot view living structures

Question 17

Compare SEM to TEM

Answer 17

Scanning electron microscope uses raster system to scan specimens line by line using a fine point beam. TEM uses broad static beam on whole image