Distance of a star from earth is 1.5 × 1011 m. If the angular size of

1.	Distance of a star from earth is 1.5 × 1011 m. If the angular size of the star is 2000’’. Find the diameter of the star.
Answer» We have, α = 200’’ = 2000 × 4.85 × 10^-6 rad. [∵ 1’’ = 4.85 × 10^-6 rad] And D= 1.5 × 10¹¹ Using d = αD, we get d = 2000 × 4.85 × 10^-6 × 1.5 × 10¹¹ = 2 × 4.85 × 1.5 × 10⁸ = 1.455 × 10⁹m.

Distance of a star from earth is 1.5 × 1011 m. If the angular size of the star is 2000’’. Find the diameter of the star.

Answer»

We have, α = 200’’

= 2000 × 4.85 × 10^-6 rad. [∵ 1’’ = 4.85 × 10^-6 rad]

And D= 1.5 × 10¹¹

Using d = αD, we get d = 2000 × 4.85 × 10^-6 × 1.5 × 10¹¹

= 2 × 4.85 × 1.5 × 10⁸

= 1.455 × 10⁹m.