# Tagged Questions

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### What happens to Newton's Third Law during the reflection of a pulse from a free end?

Well, it is known that a pulse gets inverted when it gets reflected from a fixed support while the polarity of the pulse remains same when the incident pulse gets reflected from a free end. However, ...
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### Why is everything not transparent? [duplicate]

There is a related question on this site here: Why glass is transparent? Which explains that glass is transparent because the atoms in glass have very large energy differences between energy levels ...
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### Why do different color materal differ temperature in the same sunlight?

I have a blue, red, and green cup and put a thermometer in each. Of the 3 the blue cup had the coldest temperature inside, then green, then red. I understand there may be differences in the ...
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### Fresnel equations for perpendicular angle of entry [closed]

In many text books one finds for the fresnel coefficients for light perpendicular to the surface: $$r = \dfrac{n_1 - n_2}{n_1 + n_2}\quad\text{and} \quad t = \dfrac{2n_1}{n_1 + n_2}.$$ When I try to ...
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### Number of photons through glass [closed]

I am getting mixed information on the total photon count involved with light transmission through glass. I'm not looking for percentages and I don't have equipment to count photons. For simplicity ...
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### On which factors does reflectance depend?

For my college physics project I'm planning to measure the change in reflectance of an object with respect to a factor (temperature, current going through, etc., not angle of incident, wavelength, ...
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### Standing Waves in a String of two Linear Densities

Given a string with sections of two linear densities like this: Does the point where the two linear densities meet have to be a node if a standing wave is produced? Are there alternatives? Could I ...
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### How do Hertzian dipoles relate to reflection of EM waves?

We recently performed an experiment where the intensity of microwave radiation reflected off different materials was measured. A comment in the script noted that the mechanism by which reflection of ...
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### Please explain this optical phenomenon, as seen from the top of the cup [closed]

So here is a cup, and i poured some water in it. The question is why do i see those multiple reflections? What causes these images?
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### Can decoherence occur just by simple reflection?

I create an entangled photon pair. One photon is sent inside a resonant cavity which reflects the photon many number of times. Will there be decoherence between photon in the resonant cavity and its ...
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### Why is this laser beam being scattered(and not)?

I was shining a laser beam through a liquid filled test tube(an ester particularly),and I found this phenomenon rather intriguing.Have a look. Now when I passed the laser straight through the ...
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### How does light change directions? [duplicate]

To the best of my knowledge, light will always travel at the speed of light. How then does it get reflected and change directions? Wouldn't it have to decelerate, come to a stop, and then accelerate ...
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### Why is the moon white? [duplicate]

Why is the Moon white? What is it's geological composition and how does that relate to it's apparent "color"?
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### Why does a mirror split my laser beam?

Last night my daughter was asking why a mirror "always does that" (referring to reflecting a spot of light). To help her figure it out, I grabbed my green laser pointer so she could see the light ...
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### How does the deflection of force on a tire work?

So, considering the example of a car that is turning, is all the force lost that's not along the axis of rotation of a tire, or is there some way to calculate how much of that force gets deflected ...
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### Deep confusion with conventions and signs in geometric optics

This is an equation given in my book. The question is why have they used a negative sign on the LHS? Now, if you try to derive the mirror equation with simple geometry, you get 1/v +1/u =1/f . ...
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### What happens to light when an optical cavity path length doubles instantaneously?

Let's say we have light contained in a cavity (of initial length $L$) and then instantaneously remove the second mirror, thus removing the barrier between the first and a third mirror which is some ...
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### Is it possible to save the light?

I am just thinking why can't we save the light (not a bulb). Lights normally get reflect by mirror, when source is off reflection is gone or absorbed or discharged by other object in room. Can't we ...
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### Blue hues in Aluminum mirror

[][] When depositing Aluminium sometimes I end up with a bluish hue to my film especially when changing angle of view. I use a very high rate of deposition and low temperature. What would cause this?
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### Pair of Mirrors Facing Each Other [duplicate]

If you have two mirrors facing each other and you introduce a light source into the reflections and you take the light source away, would it immediately go away for all reflections in the "tunnel" of ...
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### Reflection of light on semi-infinite solid

The following statement is often made concerning reflection on glass: "When light is normally incident on a glass surface, about 4% gets reflected and the rest is transmitted. The reflected wave is ...
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### Why is a rainbow in the sky always an arch? [duplicate]

It's been raining a lot lately in the bay area of California (thankfully! keep it coming rain gods!) which puts me and my dad in a contemplative mood. The rain has given us something to contemplate: ...
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### Is white a single color? [duplicate]

We have seen the Newton disc, when it is rotated it produces white color. So I want to know whether white exists as a single color or is that a combination of multiple colors?
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### Which Method for finding velocity of an object in the mirror is correct? [closed]

My Professor asked a question, "A person is seen jogging in a rear view mirror of focal length $1$m. He is at a distance $39$m from the mirror. His jogging speed is given to be $5 \frac{m}{s}$. ...
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### What are both way dielectric polarized mirror

I'm looking for a material that would reflect lights on one side but would allow with as little as possible filtering luminous light coming from behind. Normal both way mirror seems to filter too ...
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### What will happen in this LASER setup?

If I have 3 rectangular mirrors, say of dimensions length of 1 meter and width of 0.5 meter and I arrange them in the form of an equilateral triangle, which is of side 0.5 meter.(The mirrors are ...
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### The property of transparent lens [closed]

My question is this : what is the property of transparent material that is used for lens?. I think that it allows the light to pass through ( absorption property) and does not bend the light ( ...