(a) Describe an experiment to show how the frequency of the note emitted by a vibrating string depends on the tension in the string
(b) Draw diagrams showing a vibrating string fixed at both ends emitting (i) fundamental frequency (ii) second overtone indicate the nodes and antinodes on the diagrams
(c) With the aid of a ray diagram show how a virtual image of an object is formed by a (i) concave mirror (ii) converging lens
Explanation
(a) 
The experiment is set up as shown in the diagram. The wooden box effective length, I of the string remains constant throughout the experiment. Also the string used is of uniform thickness and must not be changed to ensure that the mass per unit length is constant throughout the experiment. The length of string is tied to the stake at one free end while a known mass is added to the other end. This creates a tension in the string which is equal to the weight of the attached mass. A tuning fork of known frequency is set vibrating and the string is tuned in unison with the fork. The frequency of the fork is recorded. The procedure is repeated by increasing the masses and using different tuning forks four more times. The corresponding tension (weights) and frequency are recorded in a table. Experiment to show that frequency is proportional to the square root of the tension, T. Mathematically, the graph of F against \(\sqrt{T}\) is a straight line through the origin.
(b)(i) 
(ii) Second overtone
(c)(i) 
(ii) 