There are two methods of transferring energy from one place to another:
(i) Through matter               (ii) Through waves

Most of the time, energy is carried out by matter. For example, when a gun is fired, the bullet gets energy through explosion and moves towards the target. The energy of the bullet is kinetic energy. On striking the target, it transfers its K.E. to it and as a result breading takes place. The energy of running water in the tunnel of a dam is also kinetic in nature. On reaching the turbine, it transfers its energy to the blades of the turbine due to which it starts rotating and produces electricity.

waves as carriers of energy

From above examples, we come to the conclusion that energy can be transferred through matter. However, matter is also displaced during this mode of energy transferred. Energy can also be transferred by wave phenomenon without transfer of matter. This can be proved by a simple experiment.


Fill a big rectangular tray with water and start up and down motion of one end of a vertical rod after dipping it in the water (fig.12.7). Transverse waves will be produced on the surface of water moving away from the position of the rod. Place a cork on the surface of water near the other end of the tray opposite to the rod. When waves pass through this cork, the cork vibrates up and down perpendicular to the water surface at its place. We impart energy in moving the rod up and down. This energy reaches the cork through water waves due to which cork vibrates. Remember that when the waves are moving the water particles do not make any forward motion along the direction of waves; they keep on vibrating at their respective places as wave passes through them. The light and heat reaches us from sun through waves.