Question

The solid angle subtended at any point inside the surface due to small area ds is given by

• A. $r^{2}ds\cos \theta$
• B. $\frac{ds\cos \theta }{r^2}$
• C. $\frac{ds\cos \theta }{r}$
• D. $\frac{r^2}{ds\cos \theta }$

Answer 1

The correct option is B $\frac{ds\cos \theta }{r^2}$

The solid angle $\Omega =\frac{A}{r^2}$

where, $A=$ area

When solid angle subtended at any point inside the surface due to small area $ds$

$A=ds$ $cos\theta$

Solid angle $\Omega =\frac{dscos\theta }{r^2}$

The correct option is B.