Physics Stack Exchange
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Questions tagged [lenses]

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually aligned along a common axis. Lenses can also focus waves other than visible light, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses.

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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 length? This is basically the standard diagram that…
Kristin
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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 the lens from the lens, and a real image occurs when…
Jonathan.
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Do people wearing glasses have different field of view than those who don't?

There is one thing I sometimes wonder about ever since I was a child. Do people who wear eye glasses see objects in different size than those who don't?(Technically different size means different projected image size on the retina.) For example do…
Calmarius
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How is a (rifle scope) reticle in focus?

The lens zooms and focuses something very far away, yet the reticle inside the lens assembly is in perfect focus just like the far objects. How?
Mark Legault
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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 to be projected onto the retina (ultimately…
wnrph
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Why does wet skin sunburn faster?

There is a popular belief that wet skin burns or tans faster. However, I've never heard a believable explanation of why this happens. The best explanation I've heard is that the water droplets on the skin act as a lens, focusing the sunlight onto…
Kendall Frey
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Why do nearsighted people see better with their glasses *rotated*?

If you are nearsighted (like me), you may have noticed that if you tilt your glasses, you can see distant objects more clear than with normally-positioned glasses. If you already see completely clear, you can distance your glasses a little more from…
Mostafa
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Are quantum effects significant in lens design?

Over on Photography, a question was asked as to why (camera) lenses are always cylindrical. Paraphrasing slightly, one of the answers and follow-up comments asserted that quantum effects are significant and that you need to understand QED in order…
Philip Kendall
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Why does aperture size affect depth of field in photography?

Why do small and big holes (the aperture) in a lens change the depth of field in the image? (if you have big hole you have smaller depth of field). I wondered if I should ask this on photo.stackexchange.com, but then realize that I want optic based…
jcubic
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Why doesn't a light ray bend again when emerging from a lens?

This image is a representation for light passing through a convex lens. It shows light entering from air to glass. When the light enters the glass we can see that it bends towards the normal. Now when the ray of light leaves the glass and enters…
Chirag Singla
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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?
user13107
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What can we deduce by the fact that mirrors cannot get a ray hotter than Sun's surface?

I think it is quite counter-intuitive that some lenses or mirrors focusing sunlight to a single spot cannot produce a temperature higher than Sun's Surface. What could a scientist deduce from that peculiar behaviour? Any quantic property in example?…
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How does a telescope make an image larger by shrinking it?

I saw these images of how a telescope works and it seems like it is shrinking the image down to the size of the eye. I don’t understand how that makes the image bigger. My thinking is that shrinking an image makes the image obviously smaller and you…
user11937382
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What is the "tangential" distortion of OpenCV actually tangential to?

I'm having a hard time understanding the distortion model of OpenCV. They use "radial" coefficients $k_n$ and "tangential" coefficients $p_n$ among others that I am not interested in. $$ x' = x (1 + k_1 r^2 + k_2 r^4 + k_3 r^6) + 2 p_1 x y +…
null
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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 the edges appear extremely brighter (brighter…
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