question_answer

Light enters at an angle of incidence in a transparent rod of refractive index of the material of the rod. The light once entered into it will not leave it through its lateral face what, so ever be the angle of incidence:

A) \[\operatorname{n}>\sqrt{2}\]                

B) n=1  

C) n = 1.1                        

D) n=1.3

Correct Answer: A

Solution :

Current through the circuit \[\operatorname{I}=\frac{E+E}{{{r}_{1}}+{{r}_{2}}+R}=\frac{2E}{{{r}_{1}}+{{r}_{2}}+R}\] \[{{\operatorname{V}}_{1}}= 0\]   (given) voltage across Ist cell is zero \[\operatorname{E}-I{{r}_{1}}=0\] \[\operatorname{E}=I{{r}_{1}}\] \[E=\frac{2E}{{{r}_{1}}+{{r}_{2}}+R}{{r}_{1}}\]                  from (1) \[E{{r}_{1}}={{r}_{1}}+{{r}_{2}}+R\] \[R={{r}_{1}}-{{r}_{2}}\]