A wave pulse, travelling on a two-piece string, gets partially reflected and partially transmitted at the junction. The reflected wave is inverted in shape as compared to the incident one. If the incident wave has wavelength  and the transmitted wave  then

While travelling from lighter medium to denser medium, a part of the incident energy gets reflected rate the lighter medium and the remaining part is transmitted into the denser medium. In this case the reflected wave suffers an additional phase change of 1800 at the interface. Also the incident wae, transmitted wave and reflected wave have the same frequency. So the incident wave is travelling in the lighter string and the transmitted wave is travelling in the denser string. sinu and   and , we can write . Also    and         v'=νλ'