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- Light is a form of energy. It travels in straight lines.
- The speed of light is constant in a vacuum. It is approximately equal to 3.0 x 108m/s.
- Light rays are regularly reflected by smooth, shiny surfaces. Images form on these surfaces. These are irregularly reflected by rough surfaces. No image forms on these surfaces.
- Light rays are refracted when they pass at an angle from one medium to another.
- Light travels in a less dense than in a denser medium.
- Sunlight separates into different colors, called the visible spectrum, as it passes through a prism. The spectrum consists of the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet.
- Dispersion is the separation of visible light into its different colors: red, orange, yellow, green, blue, indigo, and violet.
- Red, green, and blue (RGB) are the primary colors in light.
- When white light falls on an object which does not transmit light, one of the following happens:
- all of the colors in white light are reflected: the object will appear light;
- some of the colors may be reflected: the object appears colored; and
- all the colors are absorbed by the object: the object appears black.
- The colors of opaque objects are the colors they reflect and which reaches our eyes. The colors of transparent materials are the colors they transmit.