Homework Question 1.55 (6th edition)


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Shreya Tamatam 3B
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Joined: Fri Sep 28, 2018 12:25 am

Homework Question 1.55 (6th edition)

Postby Shreya Tamatam 3B » Thu Oct 18, 2018 10:27 pm

The question asks "Infrared spectroscopy is an important tool for studying vibrations of molecules. Just as an atom can absorb a photon of suitable energy to move an electron from one electronic state to another, a molecule can absorb a photon of electromagnetic radiation in the infrared region to move from one vibrational energy level to another. In infrared spectroscopy, it is common to express energy in terms of frequency/c, with the units cm-1 (read as reciprocal centimeters). a) If an absorption occurs in the infrared spectrum at 3600 cm-1, what is the frequency of radiation that corresponds to that absorption?

To answer part a, do we use the E=hv equation to solve for frequency or is another equation applicable? When I tried using this equation I got the wrong answer. Could somebody explain how they solved part a?

mahika_nayak_3L
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Joined: Fri Sep 28, 2018 12:26 am

Re: Homework Question 1.55 (6th edition)

Postby mahika_nayak_3L » Thu Oct 18, 2018 10:59 pm

Hi Shreya!

So the question asks you to solve for the frequency of radiation that corresponds with that absorption. Because the energy is given in 3600 1/cm, it is easiest to set up an equation where 3600 1/cm = v/c, as given by the problem. To solve for v, simply rewrite the equation as v=3600 1/cm * c. However, make sure that you convert the given value into meters before you plug it into the equation. This should give you 1.1 * 10^14 Hz for your answer.

Hope this helps!

Anita Wong 1H
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Re: Homework Question 1.55 (6th edition)

Postby Anita Wong 1H » Thu Oct 18, 2018 11:01 pm

You would use v/c=3600 cm^-1 v=frequency and c=speed of light
from there just plug in the speed of light and solve for v which is the frequency


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