Ans. RIPPLE TANK
Ripple tank is a device to produce water waves and to study their characteristics.
This apparatus consists of a rectangular tray having glass bottom and placed nearly half metre above the surface of a table. Waves can be produced on the
surface of water present in the tray by means of a vibrator.
This vibrator is an .oscillating electric motor fixed on a wooden plate over the tray such that its lower surface just touches the surface of water. On setting the vibrator ON, this wooden plate starts vibrating to generate plane water waves. An electric bulb is hung above the tray to observer the image of water waves on the paper or screen.