Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is (3/2) is

Question

Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is (3/2) is (A)  2 × 10-4 s (B)  2 × 108 s (C)  2 × 10-11 s (D)  2 × 1011 s

Tardigrade Admin · Accepted Answer

vg = ( c /μ ) = (3 × 108/3) = 2 × 10 8 m / s t = ( x /vg) = ( 4 × 10 -3/ 2 × 108) = 2× 10-11 s

Q. Time taken by sunlight to pass through a window
of thickness 4 mm whose refractive index is $\frac{3}{2}$ is

$2 \times 10^{- 4} s$

$2 \times 10^{8} s$

$2 \times 10^{- 11} s$

$2 \times 10^{11} s$

$v_{g} = \frac{c}{μ} = \frac{3 \times 10 ^{8}}{3} = 2 \times 10^{8} m / s$
$t = \frac{x}{v _{g}} = \frac{4 \times 10 ^{- 3}}{2 \times 10 ^{8}} = 2 \times 10^{- 11} s$

Q. Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is 23​ is

2×10−4s

2×108s

2×10−11s

2×1011s