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. $2.5\times {{10}^{8}}m/s$

Answer 1

Answer: (C)

$2.25\times {{10}^{8}}m/s$

Answer 2

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