Answer:
Speed, v = 2.82 m/s
Step-by-step explanation:
It is given that,
Mass per unit length of the rope,

Tension, T = 4 N
Wave speed, v = 2 m/s
Let v' is the speed of the wave when there is tension is doubled. The wave speed is given by :

If tension is doubled, means, T = 8 N

v = 2.82 m/s
So, if the tension is doubled, the wave speed 2.8 m/s. Hence, this is the required solution.