The focal length of field achromatic combination of a telescope is`90cm`.The dispersive powers of lenses are`0.024`and`0.036`respectively .Their focal lengths will be-

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

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

The focal length of the objective of an astronomical telescope is 1.0 m. If the magnifying power of the telescope is 20, find the focal length of the eyepiece and the length of the telescope for the relaxed eye.

An achromatic telescope objective of focal length 1.5m is consists of two thin lenses of dispersive power 0.050 and 0.075, respectively, placed in contact. Find the focal length of each lens.

A achromatic combination is made with a lens of focal length f and dispersive power omega with a lens having dispersive power of 2omega . The focal length of second will be

The length of an astronomical telescope is 40 cm. The focal lengths of its lenses will be