Analytical Chemistry UF: Comparing Wavelengths & Frequencies

In summary, the question asked for the difference in frequency between the sodium D1 line in vacuum and in air. The correct answer is 0, as both wavelengths have the same frequency. This is due to the change in speed of light between vacuum and air. The other potential response of 1.409x10^11 Hz is incorrect.
  • #1
WhoYaWitt
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Question 20 from our final I just took (Analytical Chemistry UF).

"You may recall that the wavelength of the sodium D1 line in vacuum is 589.7558nm. In air it becomes 589.5924nm. What is the difference in frequency for these two wavelengths."


I said 0. All the other people did the math for the two wavelengths and subtracted them and got 1.409x10^11 Hz.

The test was multiple choice so they were both potential responses.

Am I right in assuming that the difference in their wavelengths was due to the change in speed of light in a vacuum vs air? And that the frequency is supposed to be constant for both? Or is this not the same thing?

Thx!
 
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  • #2


Zero is the correct answer.
 
  • #3


Sweet that gives me a 95 on the final and I needed a 93 to get the A :biggrin:
 
  • #4


(and thanks for the reply as well)
 
  • #5


Your understanding is correct. The difference in wavelengths is due to the change in speed of light in vacuum and air, as you mentioned. The frequency, however, remains constant for both wavelengths. This is because frequency is determined by the source of the light, not the medium through which it is traveling. So, even though the wavelength changes, the frequency remains the same. Therefore, your answer of 0 is correct.
 

Related to Analytical Chemistry UF: Comparing Wavelengths & Frequencies

1. What is analytical chemistry and how is it different from other branches of chemistry?

Analytical chemistry is a branch of chemistry that focuses on the identification, separation, and quantification of chemical compounds in various samples. It is different from other branches of chemistry because it primarily deals with the measurement and analysis of chemical substances rather than their synthesis or production.

2. What is the relationship between wavelength and frequency in analytical chemistry?

Wavelength and frequency are two important parameters used in analytical chemistry to characterize electromagnetic radiation. Wavelength is the distance between two consecutive peaks or troughs in a wave, while frequency is the number of waves that pass a certain point in a given time. These two parameters are inversely proportional, meaning that as one increases, the other decreases.

3. How are wavelengths and frequencies used in spectrophotometry?

In spectrophotometry, wavelengths and frequencies are used to measure the absorbance or transmission of light by a sample at different wavelengths. This information is then used to determine the concentration of a specific compound in the sample. The relationship between the two parameters is described by the Beer-Lambert law, which states that absorbance is directly proportional to the concentration and path length of the sample, and inversely proportional to the intensity of the incident light.

4. Can wavelengths and frequencies be used to identify unknown substances?

Yes, wavelengths and frequencies can be used to identify unknown substances through techniques such as infrared spectroscopy and mass spectrometry. Infrared spectroscopy uses the absorption of infrared light by a sample to generate a unique spectrum, which can be used to identify the functional groups present in the sample. Mass spectrometry, on the other hand, measures the mass-to-charge ratio of ions produced by ionization of a sample, providing information about the molecular weight and structure of the unknown substance.

5. How does the use of different wavelengths and frequencies affect the accuracy of analytical measurements?

The choice of wavelengths and frequencies used in analytical measurements can greatly affect the accuracy of the results. Different compounds have different absorption or emission spectra, so selecting the appropriate wavelength or frequency for a specific compound is crucial for accurate analysis. Additionally, the presence of other compounds in a sample can interfere with the measurement, leading to inaccurate results. Therefore, it is important to carefully select the appropriate wavelengths and frequencies for each analytical measurement.

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