L3 - simple refractive optical system

Question 1

what is principle of reversibility ?

Answer 1

if location of image and object is swapped system will behave in the same way

Question 2

what sign do we use if light is travelling from left to right ?

Answer 2

positive

Question 3

what sign do we use if light is travelling from right to left ?

Answer 3

negative

Question 4

what happens to light rays coming from real object towards a spherical surface ?

Answer 4

they diverge away from source and then converge towards a real image

Question 5

what is vergence ?

Answer 5

. measure of how much a set of rays is diverging or converging
. property of bundle of rays and not individual rays
. depends on where rays originate from where they are going to

Question 6

what is the equation for object vergence ?

Answer 6

L=n/l
n= refractive index of medium
l= distance from plane of measurement to point where rays are originating from if diverging and the point they meet if converging
. l is negative if object is in left diverging

Question 7

what is the equation for image vergence ?

Answer 7

L’=n’/l’

. converging beam on right is positive thus has positive vergence

Question 8

what does L and L’ on same surface represent ?

Answer 8

L and L’ on same surface represents before and after refraction

Question 9

what is the fundamental paraxial equation ?

Answer 9

links object and image by their respective vergences
L'=L+F
L' = vergence after refraction
L = vergence before refraction
F = surface power

Question 10

what is the difference between the vergences after and before refraction by a spherical surface is equal to?

Answer 10

surface power F

Question 11

how do we know if optical surface has power ?

Answer 11

if it has the ability to change vergence upon refraction

Question 12

what does the amount of refraction depend on ?

Answer 12

refractive index between two media

in a spherical surface it also depends on the radius of curvature ( r )

Question 13

what is radius of curvature ?

Answer 13

for spherical surfaces is distance from surface to centre of curvature which is center of sphere

Question 14

what is surface power equation ?

Answer 14

F = n’-n/r

2nd refractive index - 1st refractive index / radius of curvature

Question 15

how do we find magnification ?

Answer 15

M= h’/h = L/L’

Question 16

what is object vergence when object is at infinity ?

Answer 16

l=∞ L=0

Question 17

how to calculate magnification for an object at infinity ?

Answer 17

h’= - n tan i / F

Question 18

how can we get different types of images in same optical system ?

Answer 18

.by placing object at a different distance from optical system
. e.g when object is moved closer to spherical surface image goes from being real and inverted to virtual and magnified

Question 19

what does it mean if power is positive ( F ) ?

Answer 19

image vergence L’, has higher value than object vergence L

Question 20

What is the surface power?

Answer 20

is the difference between L and L’

Question 21

What does the change in optical density show?

Answer 21

the amount of refraction we get at an optical interface