In a terrestrial telescope the focal length of erecting lens is 2 cm. The length of the telescope is 96 cm. If the magnifying power of the telescope is 10, then the focal lengths of eye-piece and objective are respectively:


Correct option is

8 cm, 80 cm






In a compound microscope the objective and eye-piece have focal lengths of 0.95 cm and 5 cm respectively, and are kept at a distance of 20 cm. The last image is formed at a distance of 25 cm from eye-piece. What is the total magnification of the microscope?       


A person cannot see objects clearly beyond 50 cm. The power of the lens to correct the vision is:


A presbyopic patient has near point as 30 cm and far point as 40 cm. The dioptric power for the corrective lens for seeing distant objects is:     


A terrestrial telescope is made by introducing an erecting lens of focal length f between the objective and eye-piece lenses of an astronomical telescope. This causes the length of the telescope tube to increase by an amount equal to:       


The length of a telescope is 36 cm. The focal lengths of its lenses can be


An astronomical telescope of ten-fold angular magnification has a length of 44 cm. The focal length of the objective is: 


A simple telescope, consisting of an objective of focal length 60 cm and a single eye lens of focal length 5 cm is focused on a distant object in such a way that parallel rays emerge from the eye lens. If the object subtends an angle of 2o at the objective, the angular width of the image is:       


Opera glasses have a minimum length of 20 cm and a magnifying power of 5 when viewing distant objects. The focal lengths of lenses used are: 


An astronomical telescope having an objective of focal length 100 cm is focused on the moon. Find the distance through which the eye-piece should be pulled back to focus an object situated at a distance 80 m from the objective:       


The diameter of the moon is 3.5 × 103 km and its distance from the earth is  seen by a telescope, having the focal lengths of the objective and the eye-piece as 4m and 10 cm respectively; the diameter of the image of the moon will be approximately: