# Homework Help: Electromagnetic radiation wavelength

1. Jul 16, 2007

An Electromagnetic radiation has a frequency of 5.00x10^14 hx.
a) Calc its wavelength in a vacuum in metres and nanometres
b)Calc its wavelength in water
c)is this radiation visible? if so wat colour?
d) What is the index of refraction of a medium in which the speed of this radiation is 2.54x10^8m/s?

My attempt...

a)c=f(wavelength) wavelength = 3x10^8/5x10^8
=600nm and 6.00x10^-7 m

b)n=1.33 in water ?=6.00x10^-7/1.33
wavelength =600nm =451nm
wavelength in median ??

c)yes this radiation is visible and according to the visible spectrum, 590-610nm is orange so its at 600nm so it is orange.

d)i cannot do this question, can anyone help me??

e)same with this one

2. Jul 16, 2007

d)c=f(wavelength)
2.54x10^8/5x10^14=wavelenngth
=5.08x10^-7m or 508 nm but that is now totally different from my other wavelength in a) this question is confusing...please help

3. Jul 17, 2007

### andrevdh

The index of refraction of a medium is the ratio of the speed of light in vacuum (air) to its speed in the medium.

The frequency stays the same in both media, it is the wavelength that changes. Your ratio is the wrong way round.

Traffic light?

Last edited: Jul 17, 2007