Question

The wavelength of red light from $He-Ne$ laser is $ 633\, nm $ in air but $ 474 $ nm in the aqueous humor inside the eye ball. Then the speed of red light through the aqueous humor is

• A. $ 3\times {{10}^{8}}m/s $
• B. $ 1.34\times {{10}^{8}}m/s $
• C. $ 2.25\times {{10}^{8}}m/s $
• D. $ 2.5\times {{10}^{8}}m/s $
• E. $ 2.75\times {{10}^{8}}m/s $

Answer 1

Answer: (C)

$ \frac{Speed\text{ }of\text{ }light\text{ }in\text{ }air}{Speed\text{ }of\text{ }light\text{ }in\text{ }aqueous\text{ }humor} $
$ =\frac{Wavelength\text{ }of\text{ }light\text{ }in\text{ }air}{Wavelength\text{ }of\text{ }light\text{ }in\text{ }aqueous\text{ }humor} $
$ \Rightarrow $ $ \frac{{{v}_{1}}}{{{v}_{2}}}=\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}} $ Or
$ {{v}_{2}}=\frac{{{\lambda }_{2}}}{{{\lambda }_{1}}}\times {{v}_{1}}=\frac{474}{633}\times 3\times {{10}^{8}} $
$ =2.25\times {{10}^{8}}m/s $