Question

The frequency of a light wave in a material is $2\times {10}^{14}Hz$ and wavelength is $5000\stackrel{\text{o}}{A}$ . The refractive index of material will be

• A. 1.40
• B. 1.50
• C. 3.00
• D. 1.33

Answer 1

Answer: (C)

Velocity of light waves in material is $v=v\lambda$ ... (i) Refractive index of material is $\mu =\frac{c}{v}$ ? (ii) where $c$ is speed of light in vacuum or air. or $\mu =\frac{c}{v\lambda }$ ... (iii) Given, $v=2\times {10}^{14}Hz$ $\lambda =5000\stackrel{\text{o}}{A}=5000\times {10}^{-10}m$ , $c=3\times {10}^{8}m/s$ Hence, from Eq. (iii), we get $\mu =\frac{3\times {10}^8}{2\times {10}^{14}\times 5000\times {10}^{-10}}=3.00$