Question

Magnification produced by astronomical telescope for normal adjustment is 10 and length of telescope is 1.1 m. The magnification when the image is formed at least distance of distinct vision (D = 25 cm) is ______.

Options

• 14

• 6

• 16

• 18

Answer 1

Magnification produced by astronomical telescope for normal adjustment is 10 and length of telescope is 1.1 m. The magnification when the image is formed at least distance of distinct vision (D = 25 cm) is 14.

Explanation:

`"f"_"o"/"f"_"e" = 10`

f_o  + f_e = 1.1

∴ f_o  = 100 cm

and  f_e = 10 cm

Final magnification = f_o `(1/"D"+1/"f"_"e")`

= 100 `[1/25+1/10]`

= 14