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sjon
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what is better ? a prism or a mirror (to reflect as much as possible wavelengths)
Mirrors & Prisms: Reflecting Wavelengths
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In summary, the question of whether a prism or a mirror is better for reflecting a wide range of wavelengths depends on the ability to make uniform and highly reflective coatings. Binoculars, which use Porro prisms, may suggest that prisms are either better or more cost-effective than mirrors for this purpose.
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tiny-tim
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Welcome to PF!
Hi sjon! Welcome to PF!
A mirror affects all wavelengths the same, but a prism affects them differently.
sjon said:
Hi sjon! Welcome to PF!
A mirror affects all wavelengths the same, but a prism affects them differently.
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sjon, if you mean a Porro prism, I think it is at least as good (if not better) than a mirror.
A Porro prism relies on total internal reflection and normally-incident transmission:
The reflections are 100%, since they are total-internal reflections. Any wavelength dependence would be in the anti-reflection coating on the front (left side) face.
Compare that to a mirror, where the wavelength dependence arises from the mirror's reflective coating.
So, the question of which is better depends on whether it's easier to make an anti-reflection or a high-reflection coating uniform AND close to 100% over a wide range of wavelengths. Anybody else have any thoughts on this?
I am thinking that since binoculars use Porro prisms, they are either better than a mirror or much cheaper than a mirror of the same performance.
EDIT:
I found a better figure than mine for showing how a Porro prism works:
http://en.wikipedia.org/wiki/Porro_prism
A Porro prism relies on total internal reflection and normally-incident transmission:
Code:
| \
------>----+--\
| |\
| |/ (90-degree angle in prism)
------<----+--/
| /The reflections are 100%, since they are total-internal reflections. Any wavelength dependence would be in the anti-reflection coating on the front (left side) face.
Compare that to a mirror, where the wavelength dependence arises from the mirror's reflective coating.
So, the question of which is better depends on whether it's easier to make an anti-reflection or a high-reflection coating uniform AND close to 100% over a wide range of wavelengths. Anybody else have any thoughts on this?
I am thinking that since binoculars use Porro prisms, they are either better than a mirror or much cheaper than a mirror of the same performance.
EDIT:
I found a better figure than mine for showing how a Porro prism works:
http://en.wikipedia.org/wiki/Porro_prism
Last edited:
FAQ: Mirrors & Prisms: Reflecting Wavelengths
What is the difference between a mirror and a prism?
A mirror is a flat, smooth surface that reflects light in a single direction, while a prism is a triangular-shaped piece of glass or plastic that refracts light into its component colors.
How do mirrors and prisms reflect and refract different wavelengths of light?
Mirrors reflect all wavelengths of light at the same angle, producing a clear and accurate reflection. Prisms, on the other hand, refract different wavelengths of light at different angles, resulting in a spectrum of colors.
Can mirrors and prisms be used to manipulate light?
Yes, mirrors and prisms can be used to manipulate light in various ways. Mirrors can be used to reflect light in a specific direction, while prisms can be used to separate white light into its component colors or to redirect light at different angles.
How are mirrors and prisms used in everyday life?
Mirrors are commonly used in households for personal grooming, decoration, and in scientific instruments such as telescopes and microscopes. Prisms are used in cameras, projectors, and in the production of rainbows.
Do mirrors and prisms have any other uses besides reflecting and refracting light?
Yes, mirrors and prisms have other uses besides their optical properties. Mirrors are used in solar power systems to concentrate sunlight for energy production, and prisms are used in fiber optics for telecommunications and medical imaging.