The tag has no wiki summary.

learn more… | top users | synonyms

3
votes
1answer
1k views

Why do focal lengths affect magnification?

For compound lenses, the image formed by first lens acts as the imaginaryobject for the second lens. In telescopes, the objective lens projects an image on its focal point which works as the object ...
2
votes
1answer
341 views

How to calculate beam spread of a non-point light source via an aspheric lens

I need to determine the angle, or rate of divergence of light from a single aspheric lens when I place a non-point light source (e.g. LED array) at a given distance from the lens which is less than ...
1
vote
2answers
533 views

How does the eye perceive a real image?

Okay, so I'm trying to grasp how the human eye will perceive the real image created for example by a convex lens. Take the upper image in this picture for example. If you were to place a screen at ...
0
votes
1answer
4k views

Magnifying Glass-How does it work? [duplicate]

How does a magnifying glass work? I know it creates a virtual image of the observed object but how is it possible that humans can see the virtual image?
3
votes
2answers
196 views

Proof that a spherical lens is stigmatic

In geometric optics, we generally allow that, for example in the case of a convex lens, rays coming from a particular point get refracted towards another particular point on the opposite side of the ...
0
votes
0answers
1k views

Why a person with a further near point experience a larger magnification with a magnifier

Two people, Micah and Lyra, with different near points are equally close to an object. Both inspect the object through the same magnifier by holding the lens close to the eye. Micah's near ...
1
vote
1answer
409 views

What determines the sign of an image distance?

A lens placed at the origin with its axis pointing along the x axis produces a real inverted image at $x = - 24 cm$ that is twice as tall as the object. What is the image distance? Why ...
5
votes
2answers
164 views

Smaller Airy disk with another lens?

Is it possible to reduce the airy disk size produced by one lens with another lens placed after the previous one? For example, parallel ray incident on first lens L1 (without aberration), then there ...
0
votes
1answer
639 views

calculating focal length of meniscus lens

As I read about telescope, distance between objective lens and eyepiece must be equal to addition of their focal lengths. D = F1 + F2 I used one of the eyepiece ...
4
votes
1answer
200 views

On the optics of high-resolution surveillance drones

In this youtube video (which is an except from a documentation I believe) a DARPA development for a high-resolution surveillance camera is presented. This question is regarding the optics that are ...
9
votes
3answers
580 views

Put a sensor at the focal length, behind, or in front?

My intuition tell me that at the focal length a convex lens all the light converges to a point. Following that logic, it would make sense to me that a camera chip would either need to go slightly in ...
1
vote
2answers
221 views

Ideal distance of eye from a lens

I observed that when I keep constant distance between object and lens but I move my eye, I get different magnification. When I am closer to lens I can see large image of the object. But if I go away ...
1
vote
2answers
343 views

Is it possible to enlarge the output angle of a projector with outside lens?

I have a very small projector, with a small output angle (30 degree). In my current demand I want a bigger output angle(90 degree), so that I can get a bigger image within a given distance. Is it ...
3
votes
2answers
406 views

Effect of gas or liquid within a compound lens system

Hi my question is if a compound lens system if filled with gas or a liquid how does it affect the system when compared to the lens system being separated by air alone. Does this affect the focal power ...
0
votes
1answer
189 views

Image Formation (Convex-Convex lenses)

I'm given with these data: Lens 1 and lens 2 are convex lenses with different focal lengths Distance of object from lens 1: 50 mm Distance between lens 1 and lens 2: 100 mm Distance of final image ...
1
vote
0answers
89 views

How does a lens affect the field of view in a mirror?

If one looks into a mirror, he can see a certain field of view. If he places a convex lens that magnifies (or a concave lens that does the opposite) in front of the mirror, but so that he can still ...
5
votes
1answer
198 views

Optics Paradox?

Imagine we have two lens, one convex and one concave, spaced in such a way that the convex lens is before the concave lens. Now each lens has its own focus length and both are spaced such that the ...
3
votes
1answer
2k views

How to find focal length of a single convex lens?

I need help finding the focal length of a single convex lens. The radius of curvature is 200mm. left side is air and the glass has a index of 1.5. I search on google but there was only formulas for ...
4
votes
2answers
2k views

How to make the projected image smaller by adding one ore more lenses in front of the built in projector lense?

I have a projector that creates a large image, even if the distance to the screen is short. The device is very small, approximateley 10x10 cm if you look from above. The height is only 3 cm. I ...
15
votes
3answers
762 views

What are these rays that appear in photograph of sun?

In many images of light emitting objects we see such rays. Why do they appear ? What is the math behind their number and direction?
-4
votes
1answer
94 views

Photonics: Slab As a Lens [closed]

The question can be found here: http://gyazo.com/fc4d26cd35e6ce368ad2a8ed504f1dcc The refractive index it references can be found here: http://gyazo.com/94fd2f3b5ea7da9226c3acd56b0024c1 I'm not ...
3
votes
1answer
387 views

How does a flat wedge lens work?

I've been seeing this lens in a lot of places especially microsoft: http://www.youtube.com/watch?feature=player_detailpage&v=rJ1p5SD3sOM#t=45s ...
0
votes
1answer
238 views

How to define the required aspherical coefficients for a lens?

I would like to purchase my own aspherical lens for testing purpose. Then I need to define the required coefficients. But how? My known requirements are f=25mm F/# 2.0 and MTF 0.5 @ 120lp/mm with a wl ...
2
votes
1answer
250 views

Curved lines in a picture (Photography)

My problem is when I take a picture (a close one) the straight edge looks a little curved. In a standard camera, like a CyberShot. I would like to know if there is some relationship between the ...
4
votes
1answer
508 views

Compound lenses and virtual images

Ok so I have this problem where I have a system of two lenses. All I know is that the distance between the object and the first lens is 30cm, the distance between the object and the final image is ...
2
votes
2answers
258 views

Do eye-glasses decrease the Depth of focus?

I was reading up about Depth of Focus and wondered if glasses affect depth of focus. If yes, is it noticeable to the user?
20
votes
1answer
6k views

Why can you see virtual images?

In optics it is widely mentioned real images are projectable onto screens whereas virtual ones can only be seen by a person. Isn't that contradictory? I mean in order to see the virtual image it has ...
2
votes
3answers
959 views

What does the optical zoom in telescopes do?

How does the optical zoom works.. Does it brings the light closer to the object... Or Does it just enlarges the picture of the object. In other words... Suppose I have telescope with 1 light-year ...