Question

When light travels from air to water, its speed is retarded by(uw = 4/3)​

Answer 1

To find:

Decrease in speed of light when it travels from air to water.

Calculation:

When any electromagnetic wave (e.g. light) travels from a rarer medium to another denser medium , its Velocity decreases.

Let speed of light in air = 3 × 10⁸ m/s.

We know that:

$\rm{ \therefore \: \mu_{w} = \dfrac{velocity \: of \: light \: in \: air}{velocity \: of \: light \: in \: water} }$

$\rm{ = > \: \dfrac{4}{3} = \dfrac{3 \times {10}^{8} }{velocity \: of \: light \: in \: water} }$

$\rm{ = > \: velocity \: of \: light \: in \: water = \dfrac{3 \times 3 \times {10}^{8} }{4} }$

$\rm{ = > \: velocity \: of \: light \: in \: water = \dfrac{9 \times {10}^{8} }{4} }$

$\rm{ = > \: velocity \: of \: light \: in \: water = 2.25 \times {10}^{8} \: m {s}^{ - 1} }$

So , decrease in Velocity be ∆v

$\therefore \: \rm{\Delta v =( 3 \times {10}^{8} ) - (2.25 \times {10}^{8} )}$

$= > \: \rm{\Delta v =0.75 \times {10}^{8} \: m {s}^{ - 1} }$

So, final answer is:

$\boxed{ \red{\: \rm{\Delta v =0.75 \times {10}^{8} \: m {s}^{ - 1} }}}$