Physics Question Pack Passage 10 Question 62 But in front of the mirror, the rays behave exactly as if they had come from behind the mirror, so that is where the image is situated.Īn experiment with light rays and a prism Obviously, if you walk behind the mirror, you cannot see the image, since the rays do not go there. ![]() This is a virtual image, since it cannot be projected-the rays only appear to originate from a common point behind the mirror. (The paths of the reflected rays into the eye are the same as if they had come directly from that point behind the mirror.) Using the law of reflection-the angle of reflection equals the angle of incidence-we can see that the image and object are the same distance from the mirror. If the rays are extrapolated backward, they seem to originate from a common point behind the mirror, locating the image. The rays can diverge slightly, and both still get into the eye. Two rays are shown emerging from the same point, striking the mirror, and being reflected into the observer’s eye. The figure above helps illustrate how a flat mirror forms an image. The two rays shown are those that strike the mirror at just the correct angles to be reflected into the eyes of the viewer. Since the movement of the light rays can be shown geometrically, if a mirror is one-half your height, you could see your whole body in the reflection. Many objects, such as people, clothing, leaves, and walls, have rough surfaces and can be seen from all sides.Ī mirror, on the other hand, has a smooth surface (compared with the wavelength of light) and reflects light at specific angles. Diffused light is what allows us to see a sheet of paper from any angle. However, light strikes different parts of a rough surface at different angles, and it is reflected in many different directions (“diffused”). We usually notice reflections off a smooth surface. The only way we can see an object that does not itself emit light is if that object reflects light. This is when a light ray, the incident ray, hits a reflective material and bounces off as the reflected ray at a specific angle. When light is bounced off of a material, such as a mirror, this is called a reflection. We'll need a few other explanations, like the one we'll cover next.The law of reflection states that the angle of reflection equals the angle of incidence. Unfortunately, a ray theory can't explain all of the behaviors exhibited by light. We take advantage of this effect to correct a person's vision or enhance it by making distant objects appear closer or small objects appear bigger. The net effect of the refraction at these two boundaries is that the light ray has changed directions. As the same ray exits, it's refracted again. As a ray of light enters the transparent material, it is refracted. Lenses serve to refract light at each boundary. A lens is a piece of glass or other transparent substance with curved sides for concentrating or dispersing light rays. ![]() Lenses, like those in a telescope or in a pair of glasses, take advantage of refraction. Diamonds have a higher index of refraction than water, which is to say that those sparkly, costly light traps slow down light to a greater degree. Diamonds wouldn't be so glittery if they didn't slow down incoming light much more than, say, water does. The amount of bending, or angle of refraction, of the light wave depends on how much the material slows down the light. When this happens, light changes speed and the light ray bends, either toward or away from what we call the normal line, an imaginary straight line that runs perpendicular to the surface of the object. ![]() Refraction occurs when a ray of light passes from one transparent medium (air, let's say) to a second transparent medium (water). This is what makes paper so incredibly useful - you can read the words on a printed page regardless of the angle at which your eyes view the surface. When light hits paper, the waves are reflected in all directions. You can see just how rough it is if you peer at it under a microscope. This scattering occurs in many of the objects we encounter every day. When light strikes a rough surface, incoming light rays reflect at all sorts of angles because the surface is uneven. Of course, we live in an imperfect world and not all surfaces are smooth.
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