Microscopy Flashcards
What is the basic theory light?
Light is electromagnetic radiation and optical microcopy makes use of visible light.
What is frequency?
the number of vibrations of a given wavelength in one second. measured in Hertz (Hz)
longer wavelengths vibrate fewer times so the longer the wavelength, the lower the frequency
How do waves travel in a vacuum?
In a vacuum, all waves in the electromagnetic spectrum travel at the same speed. This is 3x10^8.
NOT ALL WAVES TRAVEL AT THE SAME SPEED OUTSIDE OF A VACUUM!!
velocity = frequency X wavelength
What is absorption?
This is when a photon of light enters a material, but does not exit again.
this results in a thermal, electrical or chemical changes.
What is reflection?
This is when the light ray is turned back into the incident material instead of travelling on to the new material.
What is refraction?
This is when the light ray’s path is bent when it passes from one transparent material to another transparent material where its velocity changes.
What factors affect refraction?
The materials involved
The angle of the incident ray of light
The wavelength of the incident ray
What is refractive index?
It is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in a substance (v)
RI = C/V
The degree to which the light ray bends and the direction it bends are related to the refractive index value of the two substances.
What is Snell’s law?
The light ray angles and refractive indicies are related to each other by snell’s law.
What is resolution?
The ability to distinguish two points on a specimen
What is depth of focus?
The ability to maintain focus over a range of depths within the specimen, gets worse with higher magnification
What is field of view?
The size of the specimen that can be imaged at the same time
How do you calculate focussing lenses?
d = 1.22 X wavelength X. focal length/focal diameter
