The sun's angular diameter is measured to be $1920\text{'}\text{'}$. The distance of the sun from the earth is $1.496\times {10}^{11} m$. What is the diameter of the sun?

Here,

Distance of the sun from the earth, $d=1.496\times {10}^{11} m$ 

Sun's angular diameter, $\alpha =1920\text{'}\text{'}$

$$\begin{gathered} \because 1\text{'}\text{'}=4.85\times {10}^{-6} rad \\ \therefore \alpha =1920\times 4.85\times {10}^{-6} rad=9.31\times {10}^{-3} rad \end{gathered}$$

Sun’s diameter, $D=\alpha d$

       $D=\left(9.31\times {10}^{-3}\right)\left(1.496\times {10}^{11}\right)m=1.39\times {10}^{9}m$