Light
What is light and how does it travel?
Characteristics of Light
What is Light?
Light is a source of energy. Our primary source of light is the sun. Hot materials glow – like the flame in a fire. The stars, like our sun, are masses of hot gas. The light of an electric light bulb is produced from tiny, hot, glowing wire. When you look at things, what you are actually seeing is light bouncing off of objects. This is reflection.
Reflection and Refraction
How does light travel?
Light travels in a straight line. When light strikes an object, it is either reflected, absorbed, or passes through it. Objects are described as being transparent when light passes through them. Translucent objects allow some light to pass through but not all—it scatter some (think of a plastic milk carton. Objects that absorb all light or block light are called opaque.
What is reflection?
Reflection involves two rays - an incoming or incident ray and an outgoing or reflected ray. (See figure below) The law of reflection requires that two rays are at identical angles but on opposite sides of the normal which is an imaginary line (dashed in the figure) at right angles to the mirror located at the point where the rays meet. We show in the figure that the angles of incidence, I, and reflection, i', are equal by joining the two angles with an equal sign.
What is refraction?
Light’s colors are part of visible sunlight but unless a prism is used, we only see white light. A prism is a three-sided and angled object that separates light passing through it into the visible color spectrum: red, orange, yellow, green, blue, and violet. The reason this happens is that light travels at a different speeds in different materials. It's fast in air, and slower in water or glass. This has the effect of changing the direction of light, or bending it, when it moves from one material to the other. This bending of light is called refraction.