Units for Wavelengths  [ENDORSED]

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Rosamari Orduna 1D
Posts: 31
Joined: Fri Apr 06, 2018 11:04 am

Units for Wavelengths

Postby Rosamari Orduna 1D » Sat Apr 14, 2018 11:25 am

I'm doing practice problems from the text book and I notice that when calculating the wavelengths using the equation:
lambda= c/v, the units are are m.s^-1/ s, so the s cancels. Once I've divided the numbers on my calculator i get an extremely small number like (i.e. 0.000000522) how do I know how many places to move the decimal? My calculator doesnt give me the simplified version. I assume the decimal value is in m, but we want the answer in nm? Do always just move the decimal 9 places to the right??

Posts: 31
Joined: Mon Jan 08, 2018 8:19 am

Re: Units for Wavelengths

Postby tatianatumbling_1J » Sat Apr 14, 2018 1:18 pm

I believe Lavelle and the TA's prefer us to concert m to nm but if it's not specified in the problem for example "give the wavelength in nm" then either m or nm is acceptable.

Tiffany Chen 1A
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Joined: Fri Apr 06, 2018 11:02 am
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Re: Units for Wavelengths

Postby Tiffany Chen 1A » Sat Apr 14, 2018 1:33 pm

Yeah, your answer 0.000000522 (or 522 x 10^-9) is in meters and you could just leave it as meters unless the problem specifically asks for a wavelength in nanometers (or any other specific unit). If you want to convert your answer from m to nm, you can move the decimal 9 places to the right or multiply by 10^9.

Hussein Saleh 1L
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Joined: Tue Feb 20, 2018 3:01 am

Re: Units for Wavelengths

Postby Hussein Saleh 1L » Sat Apr 14, 2018 3:50 pm

Usually you'd give the answer in the desired unit. For example, some problems might say, "Give in pg". However in the rare case that the question does not tell you which unit to use, you usually want to give the same unit given in the question itself. For example, if the question states, "Find the amount of Carbon in 12.00 grams of CO2" then you're expected to find it in grams. Hope this helped!

Elena 1H
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Re: Units for Wavelengths  [ENDORSED]

Postby Elena 1H » Sat Apr 14, 2018 10:16 pm

Units depend on the question. If it asks for specific units convert to those units. If it doesn't then use whatever units are used for the given values. The important thing is to use the same units when you are actually calculating the values.

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