Question

A beam of light has frequency of $5\times {10}^{14}Hz$. How many wavelengths of this light wave are there in 0.1 mm thick glass tape $(n_{glass}=1.5)$?

• A. 100
• B. 150
• C. 250
• D. 300

Answer 1

The correct option is C 250


$t=n\lambda$
$n=\frac{t}{\lambda }=\frac{t}{\frac{v}{frequency}}$
$=\frac{\left(t\right)\left(frequency\right)}{\left(\frac{C}{RI}\right)}$
$=\frac{\left(t\right)\left(freq\right)(R.I.)}{C}$
$=\frac{{10}^{-4}\times 5\times {10}^{14}\times 1.5}{3\times {10}^8}$
$=\frac{5\times 1.5}{3}\times {10}^2$
$=\frac{5\times 150}{3}=250$