JEE Main & Advanced Physics Wave Mechanics Tuning Fork

(1) The tuning fork is a metallic device that produces sound of a single frequency.

(2) A tuning fork is really a transversely vibrating rod of rectangular cross-section bent into the shape of U as shown.

(3) The prongs execute transverse vibrations and the stem executes the longitudinal vibration. Both vibrate with the same frequency.

(4) The phase difference between the vibrations produced by both prongs of tuning fork is zero.

(5) Tuning forks are generally taken as the standards of frequency of pure notes.

The frequency of the tuning fork is given by  \[n\propto \frac{t}{{{l}^{\text{2}}}}.\sqrt{\frac{\text{Y}}{\rho }}\]

where t = Thickness of the prongs, l = Length of the prongs, Y = Young's modulus of elasticity and \[\rho =\] Density of the material of tuning fork.

(6) If one prong is broken tuning fork does not vibrate.

Effect on frequency of tuning fork

(i) A fork of shorter prongs gives high frequency tone

(ii) The frequency of a tuning fork decreases when it's prongs are loaded (say with wax) near the end.

(iii) The frequency of tuning fork increases when prongs are filed near the ends.

(iv) The frequency of a tuning fork decreases if temperature of the fork is increases.