Question 422: Ray Optics

Question

A biconvex lens of focal length $f$ forms a circular image of sun of radius $r$ in focal plane. Then

Accepted Answer

$$ 	ext { From, figure, } \quad r=f 	an \alpha $$
$$ \begin{aligned} & & &r \propto f \ & & r^2 & =f^2 	an ^2 \alpha \ & 	herefore & \pi r^2 & =f^2 	an ^2 \alpha \quad 	ext { (area of image) } \ & 	herefore & r^2 & \propto f^2 \end{aligned} $$

Answer

$\pi r^2 \propto f$.

Answer

$\pi r^2 \propto f^2$.

Answer

if the lower half part is covered by black sheet, then the area of the image is equal to $\frac{\pi r^2}{2}$.

Answer

if f is doubled intensity will increase.

Ray Optics

A biconvex lens of focal length f forms a circular image of sun of radius r in focal plane. Then

Choose the correct answer: