The wave pattern on a stretched string is shown in the figure. Interpret what kind of wave this is and find its wavelength.


Hint: We need to observe the displacement and position of different points, then accordingly nature of the two waves is decided.
Step 1: Find the nature of the wave.
Points on positions x=10, 20, 30, 40 never move, always at the mean position with respect to time. These are forming nodes that characterise a stationary wave.
Step 2: Find the wavelength.
 Distance between two successive nodes= λ2
                                  λ=2×node to node distance
                                        =2×10=20 cm