Assertion A : For light diverging from a point source, the intensity at the wavefront does not depend on the…
Assertion A : For light diverging from a point source, the intensity at the wavefront does not depend on the distance.
Reason $\mathbf{R}$ : In a diverging beam of light from a point source, spherical wavefront is observed.
(A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is true but (R) is false
(A) is false but (R) is true.
Solution
We have
$I=\frac{E}{A t}=\frac{E}{\left(4 \pi r^2\right) t} \propto \frac{1}{r^2}$
So, intensity depends on distance $\Rightarrow$ (A) is false and, for diverging beam wavefront is spherical as shown
So $(\mathrm{R})$ is true.