Question on absorbtion spectra

In summary, the atom has energy levels En=-\frac{A}{n^2} and can absorb two adjacent spectral lines at wavelengths 97.5 nm and 102.8 nm. To find the value of the constant A in electron volts, we can use the equations E_n = \frac{hc}{\lambda} = A(1 - \frac{1}{n^2}) and solve for A and n. It is also important to note that smaller wavelengths have larger energies. To find the energies at room temperature, we can assume a transition from the n quantum state to n=1.
  • #1
semc
368
5
An atom has energy levels En=-[tex]\frac{A}{n^2}[/tex] where n is an integer and A is a constant.
Among the spectral lines that the atom can absorb at room temperature are two
adjacent lines with wavelengths 97.5 nm and 102.8 nm. Find the value of the constant
A in electron volts.

Initially I thought we can equate the coulomb force to the centripetal force but we are not told the atomic number or atom. Totally no clue, how is the wavelength useful when you do not know what atom it is?
 
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  • #2
Energy of the photon absorbed or emitted is given by

[tex]E_n = \frac{hc}{\lambda} = A(1 - \frac{1}{n^2})[/tex]

Smaller wave length will have larger energy.

Write down two equations for two wavelength and solve them to find A and n.
 
  • #3
We can assume transition from n quantum state to n=1?
 
  • #4
Since the spectral lines that the atom can absorb at room temperature are two
adjacent lines with wavelengths 97.5 nm and 102.8 nm, you have to find energies of
[tex]E_n and E_{n+1}[/tex] with respect to the ground state.
 
  • #5


Thank you for your question. The absorption spectra of an atom can provide valuable information about its energy levels and can be used to identify the element. In this case, the wavelengths of 97.5 nm and 102.8 nm correspond to specific energy levels in the atom. By using the formula En=-\frac{A}{n^2}, we can calculate the energy difference between these two levels, which will give us the value of A in electron volts.

To do this, we can use the equation E=hc/λ, where E is the energy, h is Planck's constant, c is the speed of light, and λ is the wavelength. Since we are given the wavelengths, we can plug them into this equation and calculate the energy difference between the two levels. Once we have this value, we can rearrange the formula En=-\frac{A}{n^2} to solve for A.

It is important to note that the value of A will be specific to the element in question. Therefore, we will need to know the atomic number or the element itself in order to determine the value of A in electron volts.

I hope this helps to clarify the use of the absorption spectra and how it can provide information about the atom's energy levels and the value of A.
 

1. What is absorption spectra?

Absorption spectra is a graph or plot that shows the amount of light absorbed by a substance at different wavelengths. It is used to identify the specific wavelengths of light that a substance absorbs, which can provide information about its chemical composition and structure.

2. How is absorption spectra measured?

Absorption spectra can be measured using a spectrophotometer. This instrument shines a beam of light through a sample and measures the light that is transmitted through it. The difference between the intensity of the incident light and the transmitted light is used to calculate the absorbance at different wavelengths.

3. What causes absorption spectra?

The absorption of light by a substance occurs when the energy of the light matches the energy needed to excite the electrons in the substance's molecules. This causes the electrons to move to higher energy levels, resulting in the absorption of specific wavelengths of light and the creation of an absorption spectrum.

4. How is absorption spectra useful in scientific research?

Absorption spectra is used in many scientific fields, including chemistry, physics, and biology. It can be used to identify and quantify the presence of certain substances in a sample, determine the purity of a substance, and study the electronic structure of molecules. It is also useful in analyzing the composition of astronomical objects, such as stars and planets.

5. Can absorption spectra be used to identify unknown substances?

Yes, absorption spectra can be used to identify unknown substances by comparing their absorption spectra to those of known substances. If the absorption peaks and patterns match, it can provide evidence that the unknown substance is the same as the known one. However, it is important to note that other factors, such as concentration and temperature, can also affect the absorption spectra, so further analysis may be needed to confirm the identity of the substance.

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