The formula for the frequency in a stringed instrument : f=12√Tm
f = frequency; T = tension in the string; m = mass per unit lenth of the string.
f1 = 14 = 12√Tm.
When T is quadrupled, we have
f2 = new frequency = 12√4Tm
= 2(12√Tm)
= 2 f1
= 2 x 14
= 28 Hz
