## Homework Question 1.55 (6th edition)

$E=hv$

Shreya Tamatam 3B
Posts: 30
Joined: Fri Sep 28, 2018 12:25 am

### Homework Question 1.55 (6th edition)

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
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

### Re: Homework Question 1.55 (6th edition)

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
Posts: 68
Joined: Fri Sep 28, 2018 12:27 am
Been upvoted: 2 times

### Re: Homework Question 1.55 (6th edition)

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