Frequency of fork 1, no = 200 Hz No. of beats heard when fork 2 is sounded with fork 1=Δn=4 Now on loading (attaching tape) on unknown fork, the mass of tuning fork increases, So the beat frequency increases (from 4 to 6 in this case) then the frequency of the unknown fork 2 is given by, n=n0−Δn=200−4=196Hz