For example imagine we have an object in an area with wind...how the reflected light come to our eyes and doesnt travels with air (medium) ? also can the light be reflected in all directions so every observer can see it ?
3 Answers
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how the reflected light come to our eyes and doesn't travel with air (medium)?
Air is a medium for sound waves.
Unlike sound, light propagates through vacuum, which, we can say, for simplicity, is its medium.
Although, light does not need air or any other substance to get from A to B, its propagation could be affected by various substances, including air, through various types of interactions, like reflection, refraction or scattering, between photons of light and molecules of substances.
For instance, the direction of light changes, when it crosses a boundary between air and water, which have different refractive indexes.
The direction of light also slightly changes, when it passes from cold air to hot air, because the refractive index of air depends on the temperature: cold air is denser and, therefore, has a greater refractive index.
This explains the shimmer effect over a hot pavement. As the light is coming down and passes from relatively cold to relatively hot air near the pavement, it bends up and creates a distortion, which varies with the quivering of the rising air.
This is an example of how a non-uniform or moving air could visibly affect the light, but the effect of a wind, in general, may not be significant, unless it carries parcels of hot or moist air.
can the light be reflected in all directions so every observer can see it?
Sure, in fact, most non-transparent objects reflect light in all directions and can be seen from all directions.
Surfaces that reflect (or scatter) light evenly, like surfaces of carpets or sand, are called diffuse surfaces and look pretty much the same from all directions regardless of the location of the source of light.
Surfaces that reflect light mostly in one direction, where the angle of the reflected light is equal to the angle of the incident light, like surfaces of mirrors or just shiny objects, are called specular and they obviously look differently from different directions. If you look at a mirror from the direction normal to the plane of the incident light beam, you'll see very little, if anything.
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Light travels so much faster than wind or vibrating molecules. Basically the air is standing still as the photons travel through.
answered Jul 27, 2018 at 21:21
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You can do an analogy to understand it: you are in a closed room making soap bubbles, and then, somebody knocks the door.
That's exactly what happens when light travels. Light is like the knocking sound on the room, your ears on the analogy are like your eyes when you see the light, and soap bubbles are like the air molecules.
Did soap bubbles prevented you from hearing the knocking? No. Well, air itself is to light like soap bubbles are to sound: there are too few instances and they are relatively "transparent".
Wait... Light particles are not like soundwaves! In fact, they are. Did you listened out there that light can behave as a particle or a wave? It does. So, when it travels, it seems to travel as a wave, but when it interacts with an object, it might behave as a particle, like each one of your ears, in our example.
Finally, in our example, sound travels as air vibrations. Well, light photons are similar: we can say that they travel within fields, which are kind of substances that pervade everything, we are submerged within, and are fields.
There's an interesting nuance: if someone knocks at the door, air vibrations can be perceived with both ears. But that doesn't happen with light: each photon can impact only one object (e.g. atoms in your eyes). Since there are large numbers of photons impacting each one of your eyes, you cannot notice the difference. But the light you receive in your left eye is completely different to the light on the other side. Although in large quantities, it seems identical.
