Question

The distance travelled by light in glass (refractive index $=1.5$) in a nanosecond will be

• A. 45 cm
• B. 40 cm
• C. 30 cm
• D. 20 cm

Answer 1

Answer: (D)

Speed of light in glass $v=\frac{c}{\mu }$
So, distance travelled $d=c_g.t=\frac{c}{\mu }\cdot t$
$=\frac{3\times 10^8}{1.5}\times 1\times 10^{-9}=0.2m=20cm$