CBSE Class 11-science Answered

For a string the speed of the waves is a function of the mass per unit length μ = m/L of the string and the tension F in the string

If V is constant then frequency is inversly proportional to wavelength because

where is the frequency and λ is wavelength.As increases ,  decreases.

 Tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression.

To understand it think like this:

suppose a object is freely falling under gravity.Suddenly it stops.Now we know that force mg is trying to move it down but object is not moving.This is only possible if there is an upward force.This upward force can be contact force or if there is string attached then the tension force.