Correct Answer - Option 3 : 2 × 10
-11 sec
CONCEPT:
Refractive Index:
- The ratio of the speed of light in a vacuum and the speed of light in the lens material is called the Refractive Index.
\(μ=\frac{c}{v}\) or \(v=\frac{c}{μ}\)
where c is the speed of light in a vacuum, v is the speed of light in a medium.
CALCULATION:
Given:
The thickness of the slab = 4 mm = 4 × 10-3 m; refractive index μ = 1.5
- Time to pass through the glass slab:
⇒ \(t = {Distance\space travelled \over speed \space inside\space slab}= {Distance\space travelled \over \frac{c}{\mu}}\)
⇒ \(t = {4\times 10^{-3} \over \frac{3\times10^8}{1.5}}={4\times 10^{-3} \times1.5\over 3\times10^8}=2\times 10^{-11}sec\)
So, option 3rd is correct.