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Question

Physics Question on Ray optics and optical instruments

A small telescope has an objective lens of focal length 144cm144\, cm and an eye piece of focal length 6.0cm6.0\, cm. What is the separation between the objective and the eye piece?

A

0.75m0.75\,m

B

1.38m1.38\,m

C

1.0m1.0\,m

D

1.5m1.5\,m

Answer

1.5m1.5\,m

Explanation

Solution

The separation between the objective and the eye piece = Length of the telescope tube f=fo+fef = f_o + f_e Here, f0=144cm=1.44mf_0 = 144\, cm = 1.44 \,m, fe=6.0cm=0.06m f_e = 6.0 \,cm = 0.06 \,m =1.44+0.06=1.5m\therefore = 1.44 + 0.06 = 1.5\, m