# Questions tagged [reflection]

This tag is for questions relating to reflection, the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. A familiar example of reflection comes from water waves; as the waves travel they reflect off objects that are floating in the water, and also reflect off the walls of the container holding the water.

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### How does one apply the phase change of $π$ on reflection at the rigid end of a string?

Consider a string, with a free end $P$ and another end $Q$ which is rigidly fixed. Now, we start oscillating the point $P$ (with $0$ initial phase difference) and a wave starts traveling(in the ...
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### How does a rainbow show all of its colours?

My question is tied closely to this one, asked a while back on the website. As far as my understanding goes, a rainbow is formed by sunlight undergoing two refractions and a reflection inside ...
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### Dropping a mirror into a blackhole

Say you dropped a mirror into a black hole while observing at a distance and holding a clock such that the clock's face was pointing to the black hole. What is the latest time you would view on the ...
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### Why does an antinode form at the open end of an organ pipe?

I recently learnt about reflection of waves in various media and the resultant standing waves formed. In a string which is tied at an end, the wave formed reflects with a phase difference of 180 (at ...
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### How is this circular pattern of a streetlantarn behind a tree formed?

A few months ago, while walking the dog at night, I noticed a strange effect. The streetlight shining behind a barren winter tree, was somehow changed, by reflection from the branches, showed a ...
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### Why is the angle of incidence equal to angle of reflection? [duplicate]

This is true experimentally, but how do I prove this?
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### Mirror Equation for convex mirror

Question: I have a convex lens with focal length $\mathrm{70mm}$ and it's forming a real image. We have a virtual object at $\mathrm{90mm}$ to the right of the mirror. Using the mirror equation gives ...
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### Why image of vertical object is always a straight line and perpendicular to principal axis?

I am a high school student and I am very confused in geometrical optics, In all textbooks the mirror formula is derived by already assuming that the image of any vertical object (perpendicular to the ...
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### Concave mirror and convex mirror placed facing each other [closed]

A convex mirror in a concave mirror each of focal length f are placed coaxially. They are separated by 4f and their reflecting surfaces face each other. A point object is kept on the principle axis at ...
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### Alternative Schlieren parabolic mirror configuration

I have sourced two parabolic mirrors and am planning to set up a Schlieren for ultrasonic visualization and future fluids projects. A very common dual parabolic mirror configuration is the Z-type, ...
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### If diverging rays never meet, why do parallel rays meet at infinity?

I've seen that in the case of concave mirrors if the object is between focus and the pole - the reflected rays diverge and never meet. But if the object is at the focus, it's defined to be meeting at ...
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