| Question |
Answer |
| additive primary colors | Red, green, blue; form various colors when mixed in different proportions. When all three are mixed, they reflect white. |
| amplitude | The distance that a wave rises or falls from its normal rest position. |
| angle of incidence | The angle between the incident ray and the normal. |
| angle of reflection | The angle between the reflected ray and the normal. |
| beam | A very large number of individual light waves. |
| candela (cd) | The metric unit of light intensity. |
| concave mirrors | A mirror that cures like the inner surface of a sphere. |
| constructive interference | The inphase reinforcement of waves as they pass through each other. |
| crests | The highest point on a wave. |
| destructive interference | The out-of-phase cancellation of waves as they pass through each other. |
| dispersion | The separation of white light into different-color light waves. |
| electromagnetic waves | Energy in wave form that is capable of traveling through a vacuum: radio waves, microwaves, etc. |
| focal length | The distance from a lens to its principal focus. |
| frequency - The number of waves that pass a given point in one second. | |
| gamma rays | A form of radiation consisting of high-energy electromagnetic waves; electromagnetic waves that originate in the nucleus of an atom; the type of electromagnetic waves with the highest frequencies. |
| hertz (Hz) | The unit of frequency; one cycle per second. |
| incandescent | Heated to glowing. |
| incident ray | An incoming ray (toward the reflecting surface). |
| infrared waves | Electromagnetic waves with frequencies lower than visible light but greater than radio waves. |
| intensity | The measure of how bright the light from a light source is or the loudness of sound. |
| law of reflection | The angle of incidence must be equal to the angle of reflection. |
| lenses | A transparent object that uses the property of refraction to magnify or reduce images. |
| line spectrum | A display of the various frequencies of light emitted by a source. |
| longitudinal wave | A wave whose vibration is in the same direction that it is traveling. |
| mechanical waves | Rhythmic disturbances of a medium: sound waves, water waves, etc. |
| microwaves | Electromagnetic waves with wavelengths from 0.3 cm to 30 cm, and with frequencies that range from 109 Hz to 1011 Hz. |
| normal | An imaginary line drawn perpendicular to the surface of a mirror. |
| plane mirror | A flat mirror. |
| principal focus | A point through which the rays reflected or refracted from a surface will pass. |
| prism | A triangular block of glass that is used to separate visible light into various colors. |
| radar | Radio detection and ranging devices that detect objects through the transmission and reflection of microwaves off of surfaces. |
| radio waves | Electromagnetic waves with wavelengths between 1 and 10 m long and with frequencies below those visible light waves. |
| rays | Representations of the directions of light waves. |
| real image | An image that is produced in front of the plane of a mirror. |
| reflected ray | An outgoing ray (away from the reflecting surface). |
| refraction | the bending of waves as they pass from one medium into another. |
| subtractive primary color | Yellow, cyan, and magenta; when they are mixed in various proportions, they absorb all other colors except the one that is reflected. When all three are mixed together, they absorb every color, showing black. |
| transverse wave | A wave whose vibration is at right angles to the direction in which it is traveling. |
| trough | The lowest points on a wave. |
| ultraviolet light | Electromagnetic waves that are just beyond visible light in frequency. |
| velocity (v) | The rate at which an object changes position in a specified direction. |
| virtual images | The images that appear to exist beyond a mirror. |
| visible light | Electromagnetic waves with wavelengths ranging from 4 x 10-1cm to 7 x 10-5cm, and with frequencies ranging from 4.5 x 1014 Hz to 7.5 x 1014; the portion of radiant energy that can be sensed by our eyes. |
| wavelength | The distance between adjacent troughs or peaks. |
| X rays | Electromagnetic waves with frequencies higher than ultraviolet light; strong enough to penetrate body tissues. |
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