Asimple model of a strip of rubber represents it by a polymer chain consisting of n links connected end to end; each link has length a. the links all lie along the y-axis but they may be oriented in either the y or the - y direction, so that the distance l from beginning to end of the chain is much less than na. both orientations of the links have the same energy, and there is no interaction energy apart from weak thermal coupling the strip of rubber is suspended from a peg and supports a weight w. it is in thermal equilibrium at absolute temperature t. assume that the links are massless. if the number of links in the upward direction is denoted by n, the length l of the rubber is given by l (n 2n) (a) explain why, for a single link, the partition function is given by 1+exp(-2pw) and find the partition function of the system. [4 marks] (b) find expressions for the mean energy of the system and the mean value of n [4 marks] (c) hence (or otherwise) show that the equilibrium length of the strip is given by: - βλ" l n te biw