3. Two rods of different materials having coefficients of linear expansion

3. Two rods of different materials having coefficients of linear expansion α₁,α₂ and Young’s moduli  Y₁ and Y₂ respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of rods. If α_1 :α₂  =2:3, the thermal stresses developed in the two rods are equally provided Y₁ :Y₂  is equal to

(a)   2 : 3                                                      (b)   1 : 1

(c)   3 : 2                                                     (d)   4 : 9

Answer-c