Lecture 2 Microscopy Flashcards
What is refractive power and what is the formula?
How much a lens bends light.
1 diopter = 1 meter/focal length of lens
Describe the nature of a convex lens
The light will pass through the lens and converge at a focal point.
The more curved the lens, the shorter the focal length.
Continue the statement.
The shorter the focal length…
The greater the magnification
What is a focal point?
The point where the light beams converge.
Hat is focal length
The point from the center of the lens to the point where the light beams converge.
What does a short focal point mean?
The object is close to the lens which means a greater magnification.
When is a real image formed?
When the object is placed outside of the focal point.
Supply characteristics of a real image
Inverted
Can be projected onto a screen
Differs in size from the real object
What is resolution?
The ability of a microscope to distinguish two small points as separate points.
What is the resolution formula and explain each variable.
Resolution= d = 0.61 (wavelength)/ n (sin alpha)
d= distance
n= refractive index of medium
0.61= constant
Wavelength = wavelength of light (3800 A)
sin alpha = angle of cone of light entering objective lens
* the lower the d, the greater the resolution
Describe refraction of light.
As light passes through a medium it bends.
How much it bends depends on the refraction index and the angle that the light hits the service.
If the light beam strikes the medium perpendicularly the light will not bend.
The velocity also slows down when entering into a medium.
The wavelength also shortens when entering into a new medium.
Refractive Index formula (R.I.) = velocity of light/ velocity of light through the medium.
Refractive index of air = 1
How can you improve resolution?
Use a higher refractive index
Use shorter wavelengths
How is resolution accomplished
The diameter of diffraction lines around the points are reduced.
Describe a virtual image
Formed when the object is placed inside of the focal point.
Not inverted
Can’t be projected onto a screen
Can be magnified
