Question

The sun subtends an angle of half a degree at the pole of a concave mirror which has a radius of curvature of 15 m. Then the size (diameter) of the image of the sun formed by the concave mirror is

• A. 7.5 cm
• B. 6.55 cm
• C. 3.7cm
• D. 13.1cm

Answer 1

Answer: (B)

$\theta =\frac{diameterofsun}{distanceofsun}$ $\theta =\frac{diameterofimage}{focallengthofconcavemirror}$ $\frac{1}{2}\times \frac{\pi }{180}=\frac{diameterofimage}{7.5m}$ $\therefore$ Diameter of image $=\frac{\pi }{360}\times 7.5m$ $=\frac{3.14\times 7.5}{360}\times 100cm$ $=6.55cm$