Geometric optics pt II Flashcards
What is a Spherical aberration?
Deviation of rays from the paraxial approximation.
What is a Chomatic abberation?
The deviation of rays of different wavelengths due to having different indicies of refraction.
What is the aberration of Astigmatism
Foci for horizontal and vertical in different positions.
KEY METHOD
Look at GEO6 for example walkthrough
Is the magnification of an optical element equal to the size under which the eye sees an object?
NO!!!
How do we define magnification of the eye? (What is the reference point?)
Objects which are positioned in s = s0 = 25 cm in front of eye are seen with a magnification of 1. s = s0 = 25 cm called the ‘Near Point’.
The actual closest position changes with age.
What is the equation of Visual angle?
What is the equation of Angular Magnification?
Hint: Visual angle uses small angle approx tan E ~ E
How does a Magnifying glass work(Look at Next Q)? Where should the object be placed in relation to the lens? Where does the eye observe the image?
Object seems larger at infinity(Image larger than object)
What is the Angular Magnification of a Magnifying glass (when object at focal point of lens)?
This is impractical!
Aberrations would also have a large impact on images formed.
s ~ f1 and s’ ~ t is important!
What 2 lenses is a basic Microscope made of?
What do these lenses do?
Object Placed near focal point (as you approach focal point of objective lens, you produce a larger image).
What is the magnification equation of a Microscope- the information in the image maybe helpful.
Hint: Object must be placed at approx focal point of objective lens. Image from objective lens must be at the focal point of the magnifying glass/eye-piece lens.
Start with magnification of a complex optical system M = m1*m2
Example Problem GEO7
S0 = 25 cm (near point)
For a Telescope what do s, s’ and f equal?(Two of these are equal to one another)
What is the Magnification of a Telescope Objective lens?
Is the focal length short or long?
What 2 lenses are Telescopes made from and what are their properties/what do they do?
What are the rays coming from infinity like relative to one another?
What does this mean for calculating the magnification for an objective lense of a telescope?
Rays are parallel. Must use angular magnification for objective as well as magnifying glass lens.
State the Magnification of the objective and eye-piece lenses of a Telescope. State the Overall Magnification of a Telescope.
Hints:
s1 = inf –> what is s1’ in terms of focal length, use imaging eq for thin lens.
Image may be helpful.
Overall MP = -f1/f2 is what is important.
Also, seperation d = f1 + f2
Keplarian vs Galilean Telescope
Keplarian: Creates inverted image
Galilean: Creates an upright image, Shorter(in length)!
In Ray transfer matricies- what do the components of the vector of the optical beam represent? (What do y and alpha represent?)
Matrix distance Translation derivation
The bold line is the optical axis.
Derive the Translation matrix between mediums n1 and n2.
You can combine matricies for complex optical systems. Example GEO 8 - Question is on Moodle page, answer is in powerpoint. Same with Example 9
The matrix used has a general name of ‘transfer matrix’
What does it mean when A of the transfer Matrix is 0?
All incident rays with angle alpha will converge to the same point at some point y’.
What does it mean for D of the transfer matrix to be 0?
All incident rays will emerge at a single angle alpha’- rays emerge parallel.
What does it mean for C of the transfer matrix to be 0?
What does it mean for B of the transfer matrix to be 0?
