The sun (diameter D) subtends an angle of θ radians at the pole of a concave mirror of focal length f. The diameter of the image of the sun formed by the mirror is
Answer & explanation
Correct answer: option 1
Since the sun is at very large distance, p = ∞
$⇒\frac{1}{∞}+\frac{1}{q}=\frac{1}{f}$
$⇒g=f$
If the diameter of the image be
$\frac{d/2}{q}=α⇒d=(2α)q$
Putting $2α = θ$ and $q = f$
we obtain $D=fθ$
