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3
votes
1answer
657 views

Calculating minimum object distance for a lens

I am trying to figure out the Minimum Object Distance based on a simulation available here. In case you can't open it (it's a Java applet...) I'll describe it briefly. It shows an object emitting ...
1
vote
2answers
110 views

Simulating an Optical Lens

An optical lens focuses the light according to a rule (due to its special shape) and we know that rule. Now, instead of making bigger and bigger lenses, can we use an array of optical sensors and the ...
1
vote
1answer
155 views

Effect of slits and a lens

We have a screen with two slits (Young style) separated by a distance $d$, one of them receives a planar wave of $600nm$, the other receives a planar wave of $400nm$. Behind the slits there's a screen ...
1
vote
0answers
68 views

Hows lensmaker formula works? if Radius is zero?

I am doing my revision and there's such a question. However, when I tried to plug the values into the lensmaker formula, I find that one of the R is equal to zero, as it is not curved. $(n_2 ...
2
votes
2answers
91 views

What is “field size” when referring to perspective?

I'm trying to get my head around perspective. If you look at the animation in Wikipedia : You can see that the cube looks very distorted, then the edges go more parallel. From my understanding, ...
3
votes
2answers
1k views

How to draw a ray diagram from focal length, object and image heights?

Q. An object of height 8 cm is placed in front of a lens. It's inverted image of height 4.8 cm is formed on the screen. If the focal length of the lens is 12 cm then by drawing at scale calculate the ...
1
vote
1answer
990 views

Calculate the distance between two points from iPhone Camera

I want to calculate the distance between two objects using an iPhone camera. Suppose I'm standing with my iPhone 10 feet away from the objects. Now, I want to calculate the distance between those ...
1
vote
2answers
140 views

Convergence of Light on the Retina

So, I've learned about lens ray diagrams-but the problem I'm having is that when ray diagrams are drawn for a point of an image, they converge to another point, but there are two problems that I see ...
4
votes
1answer
118 views

Optics, lenses and our eyes

When we view an image, is the focal point of our eye on our retina? Shouldn't that hurt? Also, if that is how our eye works, then why don't lenses put the focal point their equivalent retina? I was ...
0
votes
2answers
492 views

Paraxial rays and marginal rays question

Paraxial rays are found to focus far away the lens whereas marginal rays focus near to the lens, why? I didn't find satisfactory answer in my academic book..
3
votes
1answer
943 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
216 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
400 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
3k 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
160 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
301 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
133 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
484 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
185 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
343 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
178 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
226 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
314 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 ...
1
vote
0answers
74 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 ...
3
votes
1answer
170 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
1k 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 ...
14
votes
3answers
588 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
81 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
334 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
211 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
215 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
442 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 ...
1
vote
2answers
173 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?
18
votes
1answer
4k 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
792 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 ...