A string is stretched between two supports that are L = 0.9 m apart. It resonates at a frequency of f = 410 Hz with a standing wave pattern that has two nodes between the two supports.

(a) Find the wavelength λ in meters.
(b) Suppose that the tension, T, in the string is increased by a factor of 4. What is the new frequency f' in Hz if the string vibrates with the same standing wave pattern as in the drawing above?

2 answers

The wire length is one half wavelength

wave speed is proportional to the square root of tension, so wave speed is doubled here.

f*lambda=speed, so if lambda is constant, speed doubled, f must...
I got the wavelength to be (2/3)L which gives you .6 and that's correct, but I can't get the second part right