The distance between the objective and eye piece of astronomical telescope in normal adjustment is 27 cm and its magnifying power is 8. What is the focal length of the objective lens?

Step-by-step solution

In normal adjustment of an astronomical telescope, the final image is formed at infinity. The length of the telescope tube is the distance between the objective lens and the eyepiece. L = f_o + f_e The magnifying power of the telescope in normal adjustment is given by: M = f_o f_e Given that L = 27 cm and M = 8 . Substituting the value of M : 8 = f_o f_e f_o = 8 f_e Substituting this relation into the equation for the length of the telescope: 8 f_e + f_e = 27 9 f_e = 27 f_e = 3 cm Now the focal length of the object