Plunk the expanded strings one after the other! Compare the sounds you could hear!
What is the relationship between the length of the string and the pitch of the fundamental tone produced by the string?

The shorter string gives a higher tone as it vibrates at a higher frequency.
The length (l) of the vibrating string equals to the half of the wavelength of the stationary wave produced on the string (2l=), so the shorter string has a smaller wavelength.

The frequency of the fundamental tone produced by the string is

,

where F is the expensive force, q is the cross-section of the string, is the density of the string material.