In a laboratory four convex lenses L₁, L₂, L₃ and L₄ of focal lengths 2,4,6 and 8 cm , respectively are available. Two of these lenses form a telescope of length 10 cm and magnifying power 4. The objective and eye lenses are respectively

Step-by-step solution

gathered Length of tube =10 ~cm array c f_o+f_e=10 ~cm Magnification m= f_o f_e =4 f_o=4 f_e array gathered Putting in Eq. (i), or 5 f_ =10 ~cm and aligned & f_e=2 ~cm & f_o=8 ~cm & f_o=8 ~cm , f_e=2 ~cm aligned Hence, L₄ and L₁ will be used.