Let’s now look at an example problem featuring specular reflection. When we have light reflecting off a flat surface in this way, it is known as specular reflection. This means that all rays coming in toward the surface at the same angle will reflect and leave The important thing to note is that, for a flat surface, the normal to the surface will be in the same direction at all We may then extend this reflected rayĪs far as we want, knowing that it will travel in a straight line. Side of the normal to the incident ray, with the same angle relative to the normal. Finally, the law of reflection tells us that the reflected ray is on the opposite We then draw the normal to the surface at We draw the incident ray up to the point where it hits the surface. We have already seen how to find the angle of reflection of The law of reflection can also be used to determine the path that a ray will follow after reflecting off a surface.įor perfectly flat surfaces, this process is straightforward. We can see that this extension of the reflected ray passes through the point marked A. We have extended the reflected ray using a red dashed line. That when it gets reflected off the mirror, the angle of incidence is equal to the angle of reflection. For each ray, we know from the law of reflection We will consider two differently angled rays coming from the object. Let’s see how this works by considering the light rays from an object when they get reflected in a mirror. This image is known as a virtual image,īecause the image is not “real” it is simply where the light rays look like they are coming from to us. We see an image of that object that appears to us to be placed behind the mirror. When we look at an object in a mirror, we know from experience that we do not see that object where it actually is. We point out that this reflected ray will be in the same plane as the incident ray but at an angle ofĤ 0 ∘ on the opposite side of the normal. So, our answer to the question is that the angle of reflection is 4 0 ∘. If we call this angle of reflection □ , then the law of reflection tells us that Recall that the law of reflection states that the angle of incidence is equal to the angle of reflection. Now that we know that the angle of incidence of the light ray is □ = 4 0 ∘, we can use the law of reflection to work We can rearrange this to make □ the subject by subtracting This 9 0 ∘ angle between the surface and the normal plus the angle We can see from the diagram that the angle of 1 3 0 ∘ is equal to Since we know that the normal to the surface is, by definition, perpendicular to the surface, we know that the angleīetween the normal and the surface itself must be 9 0 ∘. Then, the angle that we have marked □ , which is the angle of the incident ray relative to this To see how this law works, we will begin by considering the following diagram, in which a ray of light reflects off It turns out that when light reflects, it does so according to a law known as the law of reflection. And so, it is only because of this reflection that we can see them. The majority of objects around us do not emit light of their ownīut rather reflect light from an external source. The Sun or a light bulb, are relatively few and far between. Otherwise, the only things we would beĪble to see would be objects that emit light. In fact, it is only because things reflect light that we can actually see them. So, weĬould be talking about a boundary between air and water, or between glass and plastic, and so on. Recall that a medium is any material that light can travel through. There is a boundary between any two media. However, this is not the only situation in which it occurs. This process of reflection happens when light is traveling in a straight line through the air and encounters a solid Likewise, the ray of light will bounce off the object that it hits. From experience, we know that, in this case, the ball will bounce off This is the same idea as throwing a ball at a wall. Then, when we are thinking about light, we are picturing a solid objectĬolliding with another object or boundary. Traveling along the direction of that ray. To get a sense of what happens when a light ray meets an object, it may be helpful to think of light as a particle However, in reality, there is always eventually going to be some object in its path. If a particular ray of light were to never run into anything, We can recall that light rays travel in straight lines. In this explainer, we will learn how to describe the paths of light reflected from specular and diffuse surfaces,
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