wavenumber conversion

[ChemSiddiqui]

Hi I was just wondering if you can help me out on this. Note: this isn't a homework question ok!

 

How you convert the wavenumber in cm^-1 into nm. I know if it said that you had to convert that wavenumber into nm^-1 it would be X 10^10. You people think that I might have to multiply it by 10^-10?

 

Any help appreciated.

[swansont]

Multiply by 10^7

[ChemSiddiqui]

well actually i was going through it last night and I figured that we have to convert the wavenumber into frequency in nm so I used the formula V(bar) = 1/Lambda and made lambda the subject and got lambda = 1/V(bar).

 

That was 1/16300 which equalled 6.134 x 10^-5 cm. To change it into the nm scale i simply divided it by the power of 10 to -15 and the final answer came as 6.134 x 10^-15.

 

Now I don't know if its the right answer or not but my head said it is.

[swansont]

Your head's wrong. nm are smaller than cm, so there should be more of them, so your answer doesn't even pass the "reasonability" test.

 

1 cm^-1 has a wavelength of 1 cm, which is 10^7 nm.

[Bignose]

All the unit conversions are done in the same way, whether the unit is in the numerator or denominator.

 

For example, I would do this unit conversion like:

 

[math]\frac{1}{cm} \cdot \frac{1 cm}{10^7 nm} = \frac{1}{10^7 nm}[/math]

 

where the cm in the numerator and denominator cancel each other out. Note that since 1 cm = 10^7 nm, that the [math]\frac{1 cm}{10^7 nm}[/math] is equal to multiplying the term by 1.

[ChemSiddiqui]

o i see. I am shit in maths and just don't want to pay attention to some trivial things which i realise can be a disaster but i must get my acts straight in maths.