What is the wavelength of light in water when it enters a swimming pool?

[Soojin]

Homework Statement

"Light of wavelength 0.527 µm (in air) enters the water in a swimming pool. The speed of light in water is 0.700 times the speed in air. What is the wavelength of the light in water?"

Homework Equations

v = c /n, where n = 1.33 ,the index of refraction

The Attempt at a Solution

The wavelength of light in air is given. [tex]\lambda[/tex]=0.527
I looked up the speed of light in air -- 299704644.54 m/s
I also know that the speed of light in water is 0.700(299704644.54)

I am not sure how to relate these numbers to v = c/n though, or the equation to use to find the [tex]\lambda[/tex] of light in water. Can anyone offer any insight? Thanks!

 

[Doc Al]

What's the relationship between speed, wavelength, and frequency for any wave? Which of those parameters remains unchanged when light travels from one medium to another?

 

[Soojin]

What's the relationship between speed, wavelength, and frequency for any wave? Which of those parameters remains unchanged when light travels from one medium to another?

frequency = v / [tex]\lambda[/tex], so I would think the frequency would be left unchanged.

So I'm thinking I could do:

f = (speed of light in air)/0.527

to solve for the frequency, then use that value to solve for the wavelength of light in water?

 

[Doc Al]

frequency = v / [tex]\lambda[/tex], so I would think the frequency would be left unchanged.

Good.

So I'm thinking I could do:

f = (speed of light in air)/0.527

to solve for the frequency, then use that value to solve for the wavelength of light in water?

OK, but even easier is to realize that the ratio v/λ must remain fixed, so λ decreases by the same factor that the speed decreases.