Ex 1 Microscopy Flashcards
Degree of bending depends on
Refractive index and angle at which light strikes surface
How does light striking a perpendicular surface travel?
It does not bend
Refractive power
Measure of how much a lens bends light waves. Measure in diopters.
Focal point
The point through which all parallel rays of light will pass after passing through each part of the lens
Focal length
The distance from the center of the lens to the focal point
Convex lens make light rays….
converge at a focal point
Characteristics of real image
- object outside of focal point
- inverted
- can be projected on screen
- different size from object
Virtual image characteristics
- not inverted
- cannot be projected
- can be magnified
- object inside focal point
Compound microscope make….
virtual image from real image and the object will be inverted
Resolution
The ability of a microscope (or any other instrument) to distinguish small points as separate points
Resolution formula
0.6lambda/nsinalpha
How does distance affect resolution
The smaller the distance the better the resolution because the distance between the two points is smaller and we want to be able to see objects that are very close together.
We want to increase denominator and decrease the numerator.
How do you improve resolution/
Use higher refractive index or shorter wavelengths
Compound optical microscope
Light microscope, bright-field microscope
- light source
- condenser
- stage
- objective lens
- ocular lens
Pros and cons of compound optical microscope
- ability to magnify
- ability to resolve structural detail
- specimen must be thin
- relatively little contrast in unstained specimen
Phase contrast microscope
Converts phase shifts (invisible to the eye) in light passing through a transparent specimen to brightness changes (visible to eye) in the image
-can be used to examine unstained cells and tissues
-useful for examination of living cells
-
Refractive index
velocity of light inside transmitting medium
1 diopters =
1 meter divided by the focal length of the lens
How do you obtain a real image with greater magnfication?
Having the object as close as possible to the focal point of a lens with a very short focal length
When you see a virtual image, are you seeing converging or diverging rays?
Diverging- no point exists at any plane in space ta which rays radiating from the object are brought to a focus
What is the highest resolution in a light microscope? Transmission electron microscope?
Light: 0.5um (micrometers)
TEM: theoretically 0.01A realistically 5-10A (0.5-1.0nm)
Why can we not see at 0.01A using a TEM?
The electrons have refraction and bending and form clouds
So we can see molecules but we cannot see individual atoms.
Fluorescence Microscope
- detects molecules that emit light of wavelengths in visible range when exposed to UV light source
- detects naturally occurring fluorescent molecules such as Vitamin A
Most widespread use of fluorescence microscope?
- detection of antigens/antibodies in immunochemical staining procedures
- detection of fluorescent tracers injected into animals or cells
