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:

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 2^o 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:       

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:

The aperture of the largest telescope in the world is 5 m. if the separation between the moon and earth is 4 × 10⁵ km and the wavelength of visible light is 5000 Å, then the minimum separation between the objects on the surface of the moon which can be just resolved is approximately: