A guitar string of length 90 cm vibrates with a fundamental frequency of 120 Hz. The length of the string producing a fundamental frequency of 180 Hz will be ______ cm. [2023]
(60)
f=mv2l, for fundamental mode n=1
f=v2l ⇒ f∝1l
f1f2∝l2l1
⇒120180=l290 ⇒ l2=60 cm