A telescope has an objective of focal length 60 cm and eyepiece of focal length 5 cm. The telescope is focussed for least distance of distinct vision for an object 300 cm away. The linear magnification produced by the telescope is:

Step-by-step solution

For objective lens: f_o = 60 cm, u_o = -300 cm 1 v_o = 1 f_o + 1 u_o = 1 60 - 1 300 = 4 300 v_o = 75 cm m_o = v_o u_o = 75 -300 = - 1 4 For eyepiece: f_e = 5 cm, image at D = 25 cm, so v_e = -25 cm m_e = 1 - v_e f_e = 1 - -25 5 = 1 + 5 = 6 Total magnification: m = m_o m_e = - 1 4 6 = -1.5