Two waves, each of amplitude 1.5 mm and frequency 10 Hz, are travelling in the opposite directions with a speed of 20 mm/s. The distance in mm between adjacent nodes is :

(1) 1.0

(2) 1.2

(3) 1.5

(4) 2.0

**Answer: **(1) Since the amplitudes, frequency and speed of both the waves are in same, hence the wavelength of the composite wave will be the same as the single wave. The distance between the adjacent nodes will

beα2, the Speed of the wave, i.e., V = nλ. Or, 20 = 10λ. So, λ = 2 mm. Therefore,α2= 1 mm