Physics - Geometrical Optics Question with Solution | TestHub

$\text{μ}=\frac{\text{sin}{\text{θ}}_{\text{l}}}{\text{sin}{\text{θ}}_{\text{r}}}$

$\text{sin}{\text{θ}}_{\text{r}}=\frac{1}{\text{μ}}\text{sin}{\text{θ}}_{\text{i}}$

differentiate the equation with respect to θ_i.

$\text{cos}{\text{θ}}_{\text{r}}\frac{\text{d}{\text{θ}}_{\text{r}}}{\text{d}{\text{θ}}_{\text{i}}}=\frac{1}{\text{μ}}\text{cos}{\text{θ}}_{\text{i}}$

$\text{d}{\text{θ}}_{\text{r}}=\frac{1}{\text{μ}}\frac{\text{cos}{\text{θ}}_{\text{i}}}{\text{cos}{\text{θ}}_{\text{r}}}\text{d}{\text{θ}}_{\text{i}}$

$\text{Δ}{\text{θ}}_{\text{r}}=\frac{1}{\text{μ}}\frac{\text{cos}{\text{θ}}_{\text{i}}}{\text{cos}{\text{θ}}_{\text{r}}}\text{Δ}{\text{θ}}_{\text{i}}$