Problem 1.55


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deeksha1I
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Problem 1.55

Postby deeksha1I » Tue Oct 24, 2017 2:13 pm

1.55) If an absorption occurs in the infrared spectrum at 3600 cm^-1, what is the frequency of the radiation that corresponds to that absorption?

I understand that we need to use E = (v/c), and I understand how to the get the right answer once you convert the speed of light to meters. But I'm wondering why the equation won't work in meters instead of cm. Thank you!

Alissa Stanley 3G
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Re: Problem 1.55

Postby Alissa Stanley 3G » Tue Oct 24, 2017 2:56 pm

I am also struggling with this problem. How would you know to use the equation E=v/c? And why is an absorption, with units in cm, considered energy?

Gurvardaan Bal1L
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Re: Problem 1.55

Postby Gurvardaan Bal1L » Tue Oct 24, 2017 3:36 pm

Alissa Stanley 3G wrote:I am also struggling with this problem. How would you know to use the equation E=v/c? And why is an absorption, with units in cm, considered energy?


If you read the problem fully, it tells you that in infrared spectrophotometry energy is expressed in terms of v/c, which is where E = v/c comes from. The units for this is also reciprocal cm, which is where the cm^-1 comes from.

Gurvardaan Bal1L
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Re: Problem 1.55

Postby Gurvardaan Bal1L » Tue Oct 24, 2017 3:37 pm

deeksha14A wrote:1.55) If an absorption occurs in the infrared spectrum at 3600 cm^-1, what is the frequency of the radiation that corresponds to that absorption?

I understand that we need to use E = (v/c), and I understand how to the get the right answer once you convert the speed of light to meters. But I'm wondering why the equation won't work in meters instead of cm. Thank you!


This equation only works if you're using reciprocal centimeters, as that is the correct unit for this equation. I'm guessing its just because its easier to measure in centimeters.

Matthew Lee 3L
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Re: Problem 1.55

Postby Matthew Lee 3L » Wed Oct 25, 2017 1:10 am

You can do the problem using meters too. To do this, you would need to keep light as 3 x 10^8 m/s and convert 3600 cm^-1 into 360,000 m^-1. Since it is cm^-1 and not cm, you would convert it to a larger number.


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