question_answer

The sun appears to be a small disc, even though its diameter is \[\mathbf{1}{{\mathbf{0}}^{\mathbf{9}}}\] m, why?

Answer:

                The sun is at a large distance of 1011 m from  the earth. It subtends a very small visual angle (\[=\text{ 1}{{0}^{\text{9}}}/\text{ 1}{{0}^{\text{11}}}=\text{ 1}{{0}^{-2}}\]radian) at our eyes. An equal angle is subtended by a disc of \[\text{1 cm}\] diameter placed at a distance of 1 m from our eyes. So the sun appears to be a small disc.