Question

Draw a labelled ray diagram of an astronomical telescope in the near point adjustment position. A giant refracting telescope at an observatory has an objective lens of focal length 15m and an eyepiece of focal length 1 cm. If this telescope is used to view the moon, find the diameter of the image of the moon formed by the objective lens. 

The diameter of the moon is 3.42× 10⁶ m and the radius oflunar orbit is 3.8 × 10⁸m.

Answer 1

Astronomical Telescope in the near point adjustment position : 

Diameter of image of moon formed by objective lens

= af₀

= \(\frac{3.42\times10^6}{3.8\times 10^8}\) \(\times\) 15m

= 0.135 m 

= 13.5 cm