If this Telescope is Used to View a 100 M Tall Tower 3 Km Away, What is the Height of the Image of the Tower Formed by the Objective Lens? - Physics

If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?

Solution

Height of the tower, h1 = 100 m

Distance of the tower (object) from the telescope, u = 3 km = 3000 m

The angle subtended by the tower at the telescope is given as:

theta = h_1/u

= 100/3000 = 1/30 rad

The angle subtended by the image produced by the objective lens is given as:

theta = h_2/f_o = h_2/140 rad

Where,

h2 = Height of the image of the tower formed by the objective lens

1/30 = h_2/140

:. h_2 = 140/30 = 4.7

Therefore, the objective lens forms a 4.7 cm tall image of the tower.

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APPEARS IN

NCERT Class 12 Physics Textbook
Chapter 9 Ray Optics and Optical Instruments
Q 35.2 | Page 349