The subfield of optics in which light propagation is approximated in terms of rays. It mainly includes reflection and refraction on surfaces.
Questions tagged [geometric-optics]
1412 questions
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How do the laser light return from the retro-reflectors if the Earth is moving?
The U.S. and Russia routinely send laser signals to retro-reflectors that have been installed on the Moon in order to measure distances to our satellite
accurately. The Moon is slightly over one light-second away and, therefore, the round trip for a…
oadnrtyo
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8
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Can you shake your reflection's hand?
For a spherical mirror, an object at the mirror's center has an image that is also at the center. Its magnification is $-1$. For a video showing this, see here.
If you stand slightly behind the center of a large spherical mirror and hold out your…
Mark Eichenlaub
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What is the entirety of Cauchy's equation?
In my textbook it says that Cauchy's equation is
$$\mu(\lambda)=A+\frac{B}{\lambda^{2}}+\frac{C}{\lambda^{4}}+ \cdots$$
But what comes after $\frac{C}{\lambda^{4}}$? There is literally nothing given in my book as to what comes after…
RIPAN BARUAH
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Water Whirlpools - Why Uniform Shadow?
I was experimenting with creating shadows from not fully formed whirlpools, such as this one:
The direction of the light was essentially from bottom to top in this image. I think I understand most of what is happening here after I drew this…
CGS
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Are images of three-dimensional objects also three-dimensional?
Suppose that I produce an image of a dog using a converging lens. I can draw ray diagrams for the nose of the dog as well as the back leg. These are definitely longitudinal points, not transverse. However, one typically captures a two-dimensional…
Jesus
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Please tell my why the answer is not $R/2$
A ray parallel to principal axis is incident at 30° from normal on concave mirror having radius of curvature R. The point on principal axis where rays are crossing the axis is Q such that PQ is R(1-1/√3) which is not the nominal focus $R/2$. Why is…
none
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Wave theory limit of geometric optics?
Why is geometric optics the low wavelength limit of the wave theory of light? I can't seem to grasp why either a low or high wavelength limit would be necessary.
user24082
2
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2 answers
What does it physically mean for an object to be placed at infinity?
Hi Physics Stack Exchange Community. I am new to studying Optics. In my textbook there is constant mention of the images of objects placed at infinity for Concave, Convex Mirrors and Lenses. But it is unclear to me as to what is actually meant by…
Paras Khosla
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What would be the equations for the cross sections of a perfect biconvex and planoconvex lenses?
I recalled the fact that a perfect concave mirror has not a spherical surface, but a parabolic one.
I now wonder what the surface would be for a perfect planoconvex and biconvex lens (same surface mirror imaged on both sides), that can focus all…
Pritt Balagopal
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What does it mean to say image is formed at infinity?
In case of a concave mirror, when the object is at the focus, my book states that the image is formed at infinity and is highly magnified, real and inverted. But the reflected rays are parallel and will never meet, so no image will ever be formed no…
Raknos13
- 493
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Curved image in a miniscus
Reflected in a coffee cup meniscus one commonly observes a tiny image of a straight horizontal florescent lamp behind the observer quite altered. It becomes curved and changes direction with a U-turn midway somewhat like $ <,\, >\, $ shapes.
Why…
Narasimham
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What exactly is a (analytical) ray tracer in a physical sense?
I have programmed a simple 2D ray tracer for a radar signal and am now trying to understand it in physical terms. Basically, the ray tracer shoots a "shotgun" of rays from a transmitter in the general direction of a receiver, with some object(s) in…
DominikR
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How to control beam deflection through a risley prism?
I am trying to estimate the output angles for the following optical setup.
[Only for Risley Prism]
According to this source here (first orientation setup), the output beam is parallel to the optical axis, if the incoming beam is also parallel. But…
Rima
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How far away does a taller object have to be in order to appear below eye-level?
A thought experiment between a friend and I.
Let's say I'm 6ft tall, and I have a friend who's 7ft tall.
To keep things very simple for the sake of discussion, we're on a flat level plane, and I have a dumpy level.
At first, my friend is nearby, and…
Jesse Gordon
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Ray selection for field of view calculations for photodiode
The following diagram is for a photodiode:
https://www.mouser.ca/datasheet/2/313/firstsensor_PC10-2-TO5-1196700.pdf
I ran through the geometry for photodiodes using the window dimensions, die dimensions, distance of of the die to the window, and…
DKNguyen
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