Question 156: Wave Optics

Question

Two stars are 10 light years away from the earth. They are seen through a telescope of objective diameter 30 cm. The wavelength of light is 600 nm. To see the stars just resolved by the telescope, the minimum distance between them should be (1 light year = 9.46 $$ 	imes $$ 10
15
m) of the order of :

Accepted Answer

The limit of resolution of a telescope,
$$\Delta $$$$	heta $$  =  $${{1.22\,\,\lambda } \over D}$$ = $${l \over R}$$
$$ 	herefore $$   $$l$$ = $${{1.22\,\,\lambda R} \over D}$$
=   $${{1.22 	imes 6 	imes {{10}^{ - 7}} 	imes 10 	imes 9.46 	imes 10{}^{15}} \over {30 	imes {{10}^{ - 2}}}}$$
=   2.31 $$ 	imes $$ 10
8
km

Answer

10
6
km

Answer

10
8
km

Answer

10
11
km

Answer

10
10
km

Wave Optics

Two stars are 10 light years away from the earth. They are seen through a telescope of objective diameter 30 cm. The wavelength of light is 600 nm. To see the stars just resolved by the telescope, the minimum distance between them should be (1 light year = 9.46 $ \times $ 10 15 m) of the order of :

Choose the correct answer: