Question

The speed of light in water is ${\left(\frac{3}{4}\right)}^{th}$ of that in air. If the wavelength of the same light in air is $6000\AA$, its wavelength in water is :

• A. $6000\AA$
• B. $6500\AA$
• C. $4000\AA$
• D. $4500\AA$

Answer 1

The correct option is D $4500\AA$

Speed of light in water $=\frac{3}{4}$ X speed in air
$=\frac{speedinair}{4/3}$
And we know that,
Speed in water $=\frac{speedinair}{\mu }$
So, $\mu =4/3$
Now, wavelength in water $=\frac{wavelengthinair}{\mu }$
$=\frac{6000\dot{A}}{4/3}$
$=4500A^0$