| A | B |
|---|
| longitudinal wave | Molecules of the wave move in the same direction that the wave is traveling. |
| transverse wave | Molecules of the wave move in right angles to the direction that the wave is traveling. |
| amplitude | The distance from the center of the wave to a crest or a trough; measured in meters (m). |
| frequency | The number of cycles (or vibrations) that happen each second in a wave; measured in Hertz (Hz). |
| pitch | The sound we hear that is associated with different wave frequencies. Sounds with a low pitch have a smaller frequency and sounds with a high pitch have a larger frequency. |
| loudness | The sound we hear that is associated with different wave amplitudes. Softer sounds have smaller amplitudes and louder sounds have larger amplitudes. |
| compression | Part of a longitudinal wave where molecules move because they have been bumped into by the molcules next to it. |
| rarefraction | Part of a longitudinal wave where molecules move because the molucule next to it has moved and is no longer supporting it. |
| infrasonic | Sound with too low of a pitch, or less than 20 Hz, to be heard by the human ear. |
| ultrasonic | Sound with too high of a pitch, or more than 20,000 Hz, to be heard by the human ear. |
| wavelength | The distance between two crests or two troughs in a wave. |
| vibration | A back and forth motion that completes one cycle of movement; the source of all waves. |
| crest | The highest points of a wave. |
| trough | The lowest points of a wave. |
| photon | A tiny particle of electromagnetic energy that transmits light. |
| light year | The distance that light travels during one year. |
| electromagnetic wave | A wave that is caused by vibrating electric charges of atoms. |
| infrared | Electromagnetic waves of frequencies lower than the red of visible light. |
| ultraviolet | Electromagnetic waves of frequencies higher than those of violet light. |
| transparent | Materials that allow light to pas through them in straight lines. |
| opaque | Materials that absorb light and do not allow it to pass through them. |
| shadow | A shaded region that results when light falls on an object and cannot reach the space behind the object. |
