Question

when light passes through water, it’s velocity is reduced by 25%. If the speed of light in a vacuum is 1.86 x 10^5 miles per second, at what velocity does it travel through water? write your answer in scientific notation.

Answer 1

The speed of light in water is 1.395 ×
`10^(5)` miles per hour .

Explanation:

Given as :

The speed of light in a vacuum =
`v_1` = 1.86 ×
`10^(5)` miles per sec

Let The speed of light in water =
`v_2` miles per hour

When light passes through water, its speed reduced by 25%

So,
`v_2` = 1.86 ×
`10^(5)` miles per sec - 25% of
`v_1`

Or,
`v_2` = 1.86 ×
`10^(5)` miles per sec - 25% × 1.86 ×
`10^(5)` miles per sec

Or,
`v_2` = 1.86 ×
`10^(5)` miles per sec ×( 1 -
`(25)/(100)`)

Or,
`v_2` = 1.86 ×
`10^(5)` miles per sec ×
`(75)/(100)`

Or,
`v_2` = 1.86 ×
`10^(5)` × 0.75

∴
`v_2` = 1.395 ×
`10^(5)` miles per hour

So, The speed of light in water =
`v_2` = 1.395 ×
`10^(5)` miles per hour

Hence, The speed of light in water is 1.395 ×
`10^(5)` miles per hour . Answer