Question

A long glass tube is held vertically, dipping into water, while a tuning fork of frequancy 500Hz is repeatedly struck and held over the open end. Strong resonance is obtained, when the length of the tube above the surface of water is 50cm and again 84cm, but not at any intermediate point. Find the next length of the air column for resonance.

• A. 100cm
• B. 118cm
• C. 150cm
• D. 180cm

Answer 1

The correct option is B 118cm

$\frac{\lambda }{2}=(84-50)cm=34cm$
$\lambda =68cm$
b/w consecutive hormonics in a closed organ pipe the wavelength difference is $\frac{\lambda }{2}$
Next length = $84+\frac{\lambda }{2}=118cm$