| Watt: | S.I. unit for power; equivalent to joule/sec. |
| Wavelength: | The distance between the two nearest points on a wave, which are in the same phase or the distance between two adjacent crests or two adjacent troughs. |
| Wave motion: | The movement of a disturbance from one part of a medium to another involving the transfer of energy but not the transfer of matter. |
| Wave period: | The time required for two successive crests or other successive parts of the wave to pass a given point. |
| Wave velocity: | The distance traveled by a wave in one second. |
| Weight: | The force with which a body is attracted towards the center of the earth. The weight of a body of mass m is given by mg, where g is the acceleration due to gravity. |
| Weightlessness: | The state when the apparent weight of a body becomes zero. |
| Wien's displacement law: | For a black body, the product of the wavelength corresponding to maximum radiance and its absolute temperature is constant. |
| Work: | Work is done when force acting on a body displaces it. Work = Force x Displacement in the direction of the force. |
