Yikes.Molecular Expressions: Science, Optics and You - Activities in Optics - Angles of Reflection Let's count our blessings and thank the universe that Big Macs, iPhones, Cherry Cokes, and hungry zombie ninjas all reflect light. If no light bounces back from an object to our eyes, it's as if the object isn't even there. In some rare cases, light just passes through an object undisturbed, and that's what it takes to be invisible. Instead it reflects within the medium, bouncing back and forth its entire length until it finds an angle at which it may exit, at the other side. What happens is the light is at a high enough angle (with respect to the normal) within a medium that for it to refract out to the air requires an angle greater than 90, which wouldn't be in the air anyway. Fiber optics utilize total interior reflection with no light escaping a medium by refraction.
#THE ANGLE OF REFLECTION FOR THE LIGHT RAY IS HOW TO#
Scientists have learned how to capitalize on this phenomenon in communications. Next, let's talk total internal reflection. It's just as well: it'd be awful hard to study chemistry if our own (specular) reflections competed for our attention. At a microscopic level, the level at which light rays see your desk, your desk is pothole-ier than the worst of New York City's streets. The surface of a desk looks pretty flat to our eyes, but it generates diffuse reflection. Yes, that diffuse reflection is nice and abstract à la Picasso. For each scenario draw out the surface (in blue), the light rays (in red), and don't forget to draw the normal to the surface for each light ray (in black). Totally lost? Then it's time to bust out our inner Picasso and a draw a picture. These objects still reflect all of the individual light rays as described by the law of reflection, but because the surface the light rays hit is uneven, they are not all reflected back at the same angle. Objects that partake in diffuse reflection (almost everything, even you) are uneven. All of the things we see that are not shiny or "reflective," are the result of diffuse reflection. The second type of reflection is what happens with most objects. We'll talk more about mirrors in the next In Depth Section. Specular reflection is the principle behind "shiny." And at its best, as in the case of mirrors, it generates a reflection. A perfectly flat surface reflects incoming parallel light rays in such a way that they all stay parallel.
Specular reflection is what a mirror does or what we see on perfectly flat water. The next thing to know about reflection is that we distinguish between two different kinds: specular reflection and diffuse reflection. The angles of incidence and reflection are the angles between the light's direction and the normal. Are we imagining? So we're all imagining a line perpendicular to the surface of the reflecting object, we call this perpendicular line the normal. Instead, to define these angles, we have to imagine a line sticking straight out of the surface of the reflecting object. Since this is physics, these angles are not the angles between the surface of the object and the light ray. Reflection is summarized by…wait for it…the law of reflection.This law says that the angle at which light hits an object, the angle of incidence, θ i, equals the angle at which it reflects from that object, the angle of reflection, θ r. Light does exactly the same thing: it reflects. When the puck (or 8 ball or image) hits a solid object, it changes course, bouncing off at an angle. Every time we've played pool, looked in a mirror, or played ice hockey, reflection was present.
Reflection is probably the simplest property of light for us to understand because we've had good bit of experience with it.
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