L4 Flashcards
What is the image for a positive refractive surface?
object is before f so we get inverted real image and after f ( between f and refracting surface ) image becomes virtual and erect
What is the first focal point F?
the point on the optical axis such that object rays that meet or originate from this point will refract parallel to each other and to the optical axis.
What is f?
distance from surface to first focal point F
What is the 2nd focal point F’?
the point on the optical axis where image rays meet if the object rays are parallel to each other and to the optical axis.
What is f’?
distance from the 2nd focal point F’ from the surface.
Where are the F and F’ focal points on a negative spherical surface?
are on opposite sides
Where are the focal points for a negative imaging system?
1st Focal point on right and 2nd focal point on left
Where are the focal points for a positive imaging system?
1st focal point on left and 2nd focal point on right.
Where does the first focal point belong to?
object space
What does for 2nd focal point belong to?
image rays
What are single refracting systems?>
not common at all
What do most optical systems have?
2 surfaces
- Only considered air and block of glass
- simple lens with 2 spherical lenses
What happens in a simple lens with adding a second spherical surface?
refraction happening at every interface - L1, L1’, L2, L2’ plus one displacement through the lens
-Refraction happens at every surface
What does it mean that l1 is not the same as l2?
because vergence changes through displacement and this depends on the distance travel
What allows to ignore this change of vergence due to the displacement through the lens?
-the thickness of lens is d= 0 this means lens is officially thin so can ignore the change of vergence through the lens = d is small
When is d small?
the change in vergence is due to refraction only
use fundamental equation for each surface and thin lens approximation that l1,=l2
l2’ = l1 plus the change in vergence by lens itself
What is the power of thin lens given by?
sum of surface powers
F=F1+F2
What does a converging be am of light is?
Positive vergence
What does a ray of light that goes through the centre of a thin lens (in air)?
travels straight through without changing direction
where does an object appear at infinity ?
image at F’
what does the type of image in optical system depend on ?
position of object
what does location of focal point change depend on ?
depend on if its a positive or negative lens
what happens if optical media in either side of lens are same ?
. focal points are equi distance of lens
. F and F’ will have same distance but different signs
