All Questions
Tagged with refraction lenses
13
questions
44
votes
4
answers
277k
views
Virtual vs Real image
I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are.
A virtual image occurs the object is less than the focal length of ...
- 6,927
49
votes
5
answers
13k
views
If a lens focuses all incoming light to a point, how do we get 2D images?
How do lenses produce 2-dimensional images, if a lens bends all incoming rays of light to intersect at the focal point? Shouldn't this produce a single dot of light on a screen placed at the focal ...
- 601
3
votes
1
answer
418
views
Is it possible to construct a lens which focuses all the light rays from an extended object in one point?
A perfect lens focuses the light rays from an extended object (in a plane at a constant distance from the lens), in the focal plane corresponding to the distance of the object.
Now there is an ...
11
votes
2
answers
5k
views
Why do convex lenses not disperse light like prisms, given that entry and exit points aren't parallel?
I understand that light entering a parallel block of glass at a non-90 degree angle will cause dispersion of colours within the block but that these will be refracted by the same degree upon exit so ...
- 121
4
votes
1
answer
865
views
Deep confusion with conventions and signs in geometric optics
This is an equation given in my book.
The question is why have they used a negative sign on the LHS?
Now, if you try to derive the mirror equation with simple geometry, you get
1/v +1/u =1/f . I ...
- 1,770
18
votes
2
answers
2k
views
Why are the edges of the shadow so bright?
Today I noticed something while playing with my specs (having diverging lenses).
Have a look at it :
This is the shadow of my specs on the wall in sunlight. The region of the lens appears darker and ...
- 8,230
5
votes
3
answers
1k
views
Why do lens (convex) not introduce any path difference to light incident on it?
My understanding is that the top rays spend less time inside the lens where the speed of light is slow and the middle rays spend more time inside the lens so the time is kind of compensated . But I'm ...
- 153
3
votes
4
answers
7k
views
How does a Galilean telescope form an enlarged image even though it has a diverging lens?
I have been reading about Galilean telescope and the picture in the book is something like this:
After rays pass through the converging lens, there is a real image formed which is intercepted by the ...
- 99
3
votes
2
answers
51k
views
Radius of curvature and focal length
Is the radius of curvature of a convex or concave lens longer than the focal length of the lens?
Does the center or curvature affect the focal point in a lens?
- 99
2
votes
1
answer
908
views
How to graphically determine equivalent focal length of two thin lenses?
Suppose we have the schematic above. The first lens has a focal length of 80mm and the second one has a focal length of 60mm, and both are biconvex. My job is to determine, graphically the equivalent ...
- 637
1
vote
1
answer
3k
views
How does a diverging lens in a Galilean telescope form an image at infinity when its object is at its focal plane?
This is a follow up question to Farcher's answer for the question - How does a Galilean telescope form an enlarged image even though it has a diverging lens?.
Let us consider the following ray ...
- 5,306
1
vote
2
answers
660
views
How come lenses alter the path of photons?
From what I know, photons are theorized particles and believed to be massless (just energy) and travel at the speed of light. How come a lens, which is an object made of atoms, can bend a light path?
...
- 21
0
votes
1
answer
374
views
Why do we consider the optical path length constant in a Cartesian Oval
I admit that this was from a homework question, but I'm having huge trouble wrapping my head around why the optical path length needs to be the same for a Lens that focuses every single ray emanating ...
- 141