# Hydrogen Spectra: Absorbtion in White Light Explained

• harman90
In summary: This is a false statement. Absorption spectra can be observed by passing a white light. However, if We pass this Light from Hydrogen, It should not show dark lines in continuous band. The lines in line spectra are a result of the excited state of hydrogen atoms.
harman90
Absorbtion spectra can be be observed by passing a WHite light ( light containing Wavelength from appx. 400nm to 700nm).

Now here's My confusion!
if We pass this Light from Hydrogen, It should not show dark lines in continuous band. ... (as to obsorb the Light of Visible region, It's electron first need to reach the second orbit. Only then it can obsorb the frequencies of Visible region.)
now to reach second orbit, It needs wavelength corresponding to UV region, but white light doesn't have it.

I couldn't say for sure, but I have one good guess.

The transition to the first excited energy level of hydrogen is about 10eV
Boltzmann's constant times room temperature (in Kelvins) is about 1/40 eV

Using Boltzmann statistics, at room temperature, the fraction of hydrogen atoms that just happen to be in the first excited state is:
$e^{-10/(1/40)}=e^{-400}\approx 1/10^{173}$
which means it's exceedingly unlikely that even one atom in a gas cell at room temperature will absorb the white light.

However, if that vapor cell were white hot (say 58,000K), that fraction is only
$e^{-10/(20)}=e^{-2}\approx 13/100$
And a significant, fraction of hydrogen atoms will absorb and re-emit white light.

The reason that we can see the spectra at temperatures much cooler, say like the surface of the Sun (5,800K) is that there are other mechanisms that excite atoms, such as collisions with other atoms, and bombardment with stray electrons.

For example, the colored bands observed from a hydrogen lamp are a product of a huge electric field ripping electrons clean off hydrogen atoms, and the energy released when electron and proton recombine to make a hydrogen atom again.

So it means, Hydrogen shouldn't show absorption Spectra At normal temperature, But haven't heard of any such case.

They all say ... dark lines will "ALWAYS" appear corresponding to The lines in line spectra.

## 1. What is hydrogen spectra?

Hydrogen spectra refers to the unique pattern of colors or wavelengths of light that are emitted or absorbed by hydrogen atoms when they are excited. This phenomenon is a result of the specific energy levels of electrons in hydrogen atoms.

## 2. How is hydrogen spectra related to white light?

White light is a combination of all the colors of the visible spectrum. When white light passes through a hydrogen gas, some of the colors are absorbed by the hydrogen atoms, resulting in dark lines in the spectrum. These lines correspond to the specific wavelengths of light that are absorbed by hydrogen.

## 3. Why is hydrogen spectra important?

Hydrogen spectra is important because it provides evidence for the existence of energy levels in atoms, which was a key concept in the development of quantum mechanics. It also allows scientists to study the properties of hydrogen atoms and helps in identifying the chemical composition of stars and other celestial bodies.

## 4. How does the absorption of light by hydrogen atoms result in dark lines in the spectrum?

When a hydrogen atom absorbs a photon of light, the energy is transferred to an electron, causing it to jump to a higher energy level. This process is known as excitation. The electron then quickly returns to its original energy level, releasing the absorbed energy in the form of a photon. The energy of the photon corresponds to a specific wavelength of light, resulting in a dark line in the spectrum.

## 5. Can hydrogen spectra be used for practical applications?

Yes, hydrogen spectra has several practical applications. For example, it is used in spectroscopy to identify the chemical composition of substances, including the presence of hydrogen. It is also used in the study of stars and other celestial bodies, as well as in the development of new technologies such as lasers and atomic clocks.

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