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.

When a wave reaches the interface between two different media, typically some of the wave will bounce back into the original medium. This process is known as reflection.
A familiar example of reflection is optical reflection in mirrors, where light waves reflect off a smooth surface.
The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected.
Light reflects from a smooth surface at the same angle as it hits the surface. For a smooth surface, reflected light rays travel in the same direction. This is called specular reflection. For a rough surface, reflected light rays scatter in all directions. This is called diffuse reflection.

1877 questions
42
votes
3 answers

Why does a mirror reflect visible light but not gamma rays?

Visible light (~500 THz) as well as gamma rays (~100 EHz) are electromagnetic radiation but we can reflect visible light using a glass mirror but not gamma rays. Why is that?
38
votes
2 answers

Should a superconductor act as a perfect mirror?

I have been told that metals are good reflectors because they are good conductors. Since an electric field in conductors cause the electrons to move until they cancel out the field, there really can't be electric fields in a conductor. Since light…
37
votes
4 answers

Why are the edges of a broken glass almost opaque?

Unfortunately I broke my specs today which I used in this question . But I observed that the edges are completely different then the entire part of the lens. The middle portion of the lens was completely transparent but the edges appeared opaque…
Ankit
  • 9,249
37
votes
4 answers

Why do photons follow specific path after reflection from a mirror surface if they can be emitted in any direction by electrons of mirror surface?

The electron absorbs the energy of photon(with specific frequency)and re-emits the photon.The photon can be emitted in any direction. So why do they get re-emitted in a specific direction after reflection? On hitting normal to surface the photons…
37
votes
6 answers

If the moon had a mirror surface, would the earth be equally illuminated as by the sun during full moon, or would it require a different mirror shape?

Suppose the apparent diameters of the sun and the moon are exactly the same (which in fact very close to the real situation). If the moon had a perfect mirror surface, would the reflected visible light of a full moon (at night) illuminate the earth…
35
votes
4 answers

Explain reflection laws at the atomic level

The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction?
35
votes
3 answers

Why is the light reflected at the same angle from mirror?

From the school physics I know that the material objects bounce from the plane surface at the same angle, losing some kinetic energy. In the same school I was taught that the light (and waves in general) obeys this principle too. Obviously, in the…
abyss.7
  • 555
34
votes
6 answers

Why do reflections on a rough surface stretch from the light source towards you instead of spreading out in all directions?

When light reflects off a "flat ground" surface, the reflection stretches vertically but not horizontally (as shown in the pictures below). When light reflects off a "vertical wall" surface, the reflection stretches horizontally but not vertically.…
clickbait
  • 589
34
votes
6 answers

Why did high quality mirrors use aluminum coatings instead of silver?

I have two questions on mirrors. I’ve read that in the past quality mirrors were coated with silver but that today vacuum evaporated coatings of aluminum are the accepted standard. When I look at the reflectance vs. wavelength plot , I see that…
Carlos
  • 4,648
32
votes
3 answers

How can a virtual image form a shadow?

This is something that completely blew my mind. Last week I was playing randomly with a mirror and my pen and then I noticed that the image of the pen was also having its shadow on a nearby wall. How is that even possible? For something to form a…
Ankit
  • 9,249
32
votes
3 answers

Why is reflected light polarised?

Why is reflected light polarised? I have learnt about Brewster's angle, and how at a particular angle all light reflected is polarised, but do not understand why. Is this something that could be explained to a guy that doesn't have a Ph.D in physics?
31
votes
3 answers

A Rainbow Paradox

I was studying the phenomena of the formation of a rainbow. In my book, the following diagram is given: So, the rays at the red end of the spectrum make a larger angle with the incident ray than the rays at the violet end of the spectrum. However,…
31
votes
12 answers

Why is everything not invisible if 99% space is empty?

If every object is $99$ % empty space, how is reflection possible? Why doesn't light just pass through? Also light passes as a straight line, doesn't it? The wave nature doesn't say anything about its motion. Also, does light reflect after striking…
30
votes
8 answers

Why is angle of incidence equal to angle of reflection?

In the Law of Reflection, the angle of incidence is equal to angle of reflection. Why is this true? This is clearly true experimentally, but how does one prove this true mathematically?
Gamira
  • 525
30
votes
1 answer

How are photons "consumed"?

I have very little background in physics, so I apologize if this question is painfully naive. Consider the following thought experiment: an observer is in a closed room whose walls, floor, and ceiling are made entirely of mirrors, with a single…