# Tag Info

1 vote

### What is the theoretical range of temperature the air must be in order to reflect/refract light (for a volumetric display)?

To do what you are suggesting would require changing the index of refraction of the air significantly by heating and cooling localized points in space. The temperature dependence of the index of ...
1 vote

The general solution to the time-harmonic wave equation on a string may be written as $$y(x,t)=\sin(\omega t)\left[A\sin(kx) + B\cos(kx)\right].$$ The condition at $x=0$ is that $y(0,t)=A_0\sin(\omega ... • 1,109 1 vote Accepted ### How does a rainbow show all of its colours? The diagram produced in the question has a couple of errors and almost answers the question. To a very good approximation the rays coming from the Sun are approximately parallel and the reflection ... • 77k 1 vote ### How does one apply the phase change of$π$on reflection at the rigid end of a string? The Phet Wave on a string simulation is worth a look at with oscillate chosen. You can also change the damping, tension, frequency etc to look further at what happens when there is a fixed end. At the ... • 77k 0 votes ### How does a rainbow show all of its colours? The graphics just shows two raindrops, although of course there are lots of raindrops in between those two. It shows that every raindrop emits a bunch of rays, dispersed depending on the wavelength (... • 2,048 0 votes ### How does a rainbow show all of its colours? When light hits the edge of the bubble (from the inside as well as from the outside), it can undergo a reflection as well as a refraction. So there can be several reflections inside the bubble before ... • 613 2 votes ### Dropping a mirror into a blackhole The first and second inequality/equation in ProfRob's answer here is the answer to your question. I'm posting this as an answer instead of a suggested duplicate because the questions are distinct and ... • 8,478 0 votes ### Dropping a mirror into a blackhole The clock will measure the proper time of an observer falling into the black hole. The observer will reach the horizon in a finite proper time; you will observe the clock reaching this value ... • 33.3k 1 vote Accepted ### Why does an antinode form at the open end of an organ pipe? There are two ways of describing a sound wave. As a (variation of displacement) wave and as a (variation of) pressure wave. You will note that there is a$\pi/2$phase difference between these two ... • 77k 1 vote ### Why does an antinode form at the open end of an organ pipe? I think you may be a bit confused. For both string and tube, a closed end should give a node and an open end an antinode. You may be mixing up displacement and pressure (or force). A node for ... • 695 2 votes ### How is this circular pattern of a streetlantarn behind a tree formed? The branches may be randomly oriented, but the light is only strongly reflected perpendicular to the direction of the branch. Those branches that point more or less toward the lamp (from your ... • 33.7k 0 votes ### Images formed by a pair of plane mirrors Actually only 5 images will be formed if more images are drawn they will overlap the existing ones if drawn with perfect geometry. • 3 2 votes Accepted ### Mirror Equation for convex mirror What you have done is correct. We have to judge the diagram by obtaining the results from the formula but not just simply imagining a diagram. The results suggest that your diagram was wrong and the ... • 267 0 votes Accepted ### Concave mirror and convex mirror placed facing each other You are struggling with sign convention in optics. That is really frustrating. In the figure$l$,$x$and$f_0$are all positive (as they should be in normal world) Applying mirror equation for first ... • 415 -1 votes ### Why image of vertical object is always a straight line and perpendicular to principal axis? So I think what you mean is why is the image assumed to be perpendicular to the surface it is standing on... And it is not slanted or curved as you have demonstrated in your second diagram. My ... 1 vote ### Why image of vertical object is always a straight line and perpendicular to principal axis? The answer is that all points with the same distance$u$image onto different points but with the same distance$v$. You can ask, "ok, but why", and the proof to that is actually not shown ... • 3,724 -1 votes ### Why image of vertical object is always a straight line and perpendicular to principal axis? You draw it vertical because you are looking at your screen that is vertical (perpendicular to the optics axis). Edited: it's due to the fact that a lens in the optical limit has a focus$f$and if ... 1 vote ### If particles are also waves cant we invert them by making it reflect off a fixed boundary? There is a very nice answer by @annav, I would like to add something interesting. A very nice example of what you are asking for is when a photon (or classically light) gets reflected off a surface (... • 25.4k 4 votes Accepted ### Rainbow reflections from salt crystals I suspect the rainbow is from retroreflector glass beads rather than salt. Tiny glass beads are placed on the surface of road markings, halfway embedded, making them reflect light from vehicles back ... • 26.8k 1 vote ### Rainbow reflections from salt crystals Looks like, e.g., ice crystals can cause some rainbow-like effects. So maybe salt crystals or some other crystals can cause the effect in your video. It seems that in your video the rainbow is present ... • 23.6k 2 votes ### If particles are also waves cant we invert them by making it reflect off a fixed boundary? I see your intuition that cancelling waves are analogous to particle-antiparticle annihilation, but quantum state of an antiparticle is not just a$180^\circ$phase shift of the quantum state of a ... 1 vote ### If particles are also waves cant we invert them by making it reflect off a fixed boundary? In quantum mechanics , particles are described by wave functions, which represent the probability that a particle is found in vicinity of point (x,y,z). Now, suppose you have a barrier whose task is ... 8 votes ### If particles are also waves cant we invert them by making it reflect off a fixed boundary? The elementary particles are described by quantum mechanical equations , wave equations but the solutions are not waves in the (x,y,z, t) of the particle but of the probability to find the particle ... • 221k 21 votes Accepted ### If particles are also waves cant we invert them by making it reflect off a fixed boundary? Here is a simulation of the Schrödinger equation I made a while ago: In the gif you see the Schrödinger equation for a single, one-dimensional particle. The particle moves on the left-to-right axis ... 0 votes ### Law of reflection in vector form: how is$\vec{n}_2 = \vec{n}_1 - 2(\vec{n}_1 \cdot \vec{s}) \vec{s}\$ derived?

we are given unit vectors i, n and r. Lets consider vector t perpendicular to n and parllel to mirror/tangent. ...
Accepted

### Sunscreen protection, SPF, and amount applied: relationship?

A sunscreen's sun protection factor (SPF) is defined as $$\frac{\text{minimal erythemal dose in sunscreen-protected skin}}{\text{minimal erythemal dose in non-sunscreen-protected skin}},$$ so its ...
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