Microscope/telescope Flashcards
microscope
- 2 lens system
- real converging, inverted, magnified
total magnification of microscope
Mtot=M1 x M2 (essentially squared)
image and rays at the eye piece
-the parallel rays NEVER converge, the image is at optical infinity, can not ray trace the image, virtual optical infinity
final image through microscope
has magnification substantially more than 1
magnification of eye piece!!
Mep= 25cm/fe+1
eye piece is essentially a magnifying lens
microscope magnification
M=M(objective) x M(eye piece) = (- L/f0) x (25cm/fe)
resolution limit
- how sharp/clear an image is
- tell the difference between two points
- minimum angle of resolution (MAR), the smaller the better!
- expressed in angles or length
resolving power (ability)
- 1/resolution
- reciprocal of the resolution limit
- LARGER is better
- expressed in inverse angles, or inverse length
what does resolution depend on?
wavelength
what can the human eye resolve
around 1 arcmin
useful magnification
- eye can only pick up so much
- no sense in over magnifying if eye can’t pick it up
- about 0.25m (near point)
what is a telescope?
two lens system
What is the image of the first lens in the telescope?
the object for the second lens.
What is the first lens in a telescope?
objective lens
what is the second lens in a telescope?
the eye piece
What is the beam vergence of incoming rays in telescope?
collimated, 0 beam vergence
what is the beam vergence of outgoing rays in a telescope?
collimated, 0 vergence
Where is the object located in telescope?
optical infinity
What is the difference between the two collimated incoming/outgoing rays?
the incoming rays have a much larger diameter than the outgoing rays
What does a telescope ultimately do?
condense large things into smaller rays of light
What is the total optical power of a telescope?
0
-0 beam veregence coming in and going out
Po+Pe-(d/1)Po(Pe)=0
where are the principal planes of a telescope?
at infinity
magnification of telescope
-microscope and the telescope are based on magnification of a magnified image, and thus the total magnification is the product of the two individual magnifications, the primary, from the objective lens, and the secondary from the eye piece
What kind of vergence does a microscope have?
strong vergence
what kind of vergence does a telescope have?
no vergence
What do you observe with a microscope?
a near object
what do you observe with a telescope?
distant object
lens separation in a microscope
larger than the sum of the focal distances
lens separation in a telescope
equal to sum of the focal distances
what are the properties of an image seen through a microscope?
-magnified, inverted, dimmer
what are the properties of an image seen through a telescope?
- minified, inverted, brighter
- changes apparent angle in which we view the object
is the telescope actually magnifying?
- contrary to a microscope, the telescope lateral magnification is smaller than 1: we may observe a real image of the sun projected o a screen with a telescope
- the image’s diamter is far smaller than that of the sun, and thus the lateral magnification is a very small number
- this image, however is perhaps 20 to 50 times larger than what it would appear through the naked eye
What sets the limit of resolution in any optical system?
-diffraction from circular aperature
minimum angle of resolution
=(1.22 X wavelength)/(objective lens diameter)
telescope resolution
- we unsuccessfully observe a double star with a telescope (no double star resolution)
- to improve resolution, we decide to employ a chromatic filter
- You want the angle of resolution to be at it’s smallest, so put a blue filter on to make the angle smaller
smaller angle of resolution…
larger objective lens diamter
Why do some stars appear as 1, when there are acatually 2 or 3?
because the angle of resolution is so small you cannot differentiate
What can the eye resolve?
about 1’
what can a telescope resolve?
about 1”
Kepler type telescope
- astronomical
- length of telescope is the focal length
- two plus lenses
- virtual image at optical infinity
- d=Fo+Fe
Galilei type telescope
- terrestrial
- low vision aids in optometry
- erect image at optical infinity
- d=Fo-Fe
What lens has the biggest diameter in a kepler type telescope?
objective lens
What lens has the biggest power in a kepler type telescope?
eye piece
What is a problem with using a very large diameter lens?
weighgt, cost
galilei type telescope and visual aid
- erect shorter image
- 2 lenses, not fused, there is air between them
newtonian refractor
defflector on side
catadioptric telescopes
combo of mirrors and optics
What is chromatic abberation related to?
refraction
how many surfaces in reflecting telescopes?
1
Where is the support needed in a reflecting telescope for the lens?
in the back
why do stars twinkle?
the atmosphere is a nonuniform lens scattering the layers
a telescope can only be as good as…
the atmospheric conditions
adaptive optics
-atmospheric turbulence can cause distorted wavefront
