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:       

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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:       


Correct option is


The minimum distance between the real object and real images is 4f.



A liquid is placed in a hollow prism of angle 60o. If angle of minimum deviation is 30o, what is the refractive index of the liquid?     


We have a right-angled isosceles prism. Its refracting index is 1.5. If a ray is incident normally on one of the two perpendicular surfaces which of the following phenomena will take place?    


A beam of light consisting of red, green and blue colours is incident on a right-angled prism. The refractive indices of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47 respectively. The prism will:


If the ratio of magnifications produced by a simple microscope in near point adjustment and far point adjustment is 6/5, then the focal length of the lens is (take D = 25 cm):    


When the length of a microscope increases its magnifying power:


The focal length of the objective and the eyepiece of a compound microscope are 1 cm and 5 cm respectively. An object is placed at a distance of 1.1 cm from the objective. If the final image is formed at the least distance of distinct vision, the magnifying power is:        


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:     


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