An optical engineering question firm needs to ensure the separation between two mirrors is unaffected by temperature changes. The mirrors are attached to the ends of two bars of different materials that are welded together at one end as shown in figure. The surfaces of the bars are lubricated. If the coefficient of linear expansions of the two rods ( of initial length L_(1) and L_(2) ) are alpha_(1) and alpha_(2) respectively and L is the distance between the two mirrors initially, then

An optical engineering question firm needs to ensure the separation be

1.	An optical engineering question firm needs to ensure the separation between two mirrors is unaffected by temperature changes. The mirrors are attached to the ends of two bars of different materials that are welded together at one end as shown in figure. The surfaces of the bars are lubricated. If the coefficient of linear expansions of the two rods ( of initial length L_(1) and L_(2) ) are alpha_(1) and alpha_(2) respectively and L is the distance between the two mirrors initially, then
Answer» `L_(1) = ( L alpha_1)/( alpha_2 - alpha_1)` ` L_1 = ( L alpha_2)/( alpha_2 - alpha_1)` `L_2 = ( Lalpha_1)/( alpha_2 - alpha_1)` `L_2 = ( L alpha_2)/( alpha_2 - alpha_1)` ANSWER :B