# Spectral Series

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Light is one of the most prominent topics in Physics. Several studies explained various things about the light, how it travels, how it reflects etc., and many more. One of the other important concepts is the spectral series. Let us understand the spectral series and spectral series of hydrogen atoms.

The spectral series is in the form of lines. Whenever the atoms of an element get excited and emit the light rays from higher energy levels to lower energy levels, these can be calculated using the Rydberg formula.

## Spectral Series of Hydrogen Atoms

Studying the hydrogen atom is the easiest way of understanding the principle of spectral series. It is the simplest atom that we can get to observe the spectral series. To observe these series of the spectrum, we need to send a beam of light into the slit. Every component of this beam of light may form a different image which can appear as some spectral series when the images are exposed to a spectroscope.

These spectral series are like parallel lines with uniform distance and speed. The wavelength of light can influence these spacings if the wavelength of spectral lines is higher and the spacing is more, and the lines are visible like they are apart from each other. On the other hand, if the wavelength is less, the lines also come closer and seem to be beside each other. If the shortest wavelength is recorded, then the distance between the lines was also recorded. This is called the series limit. By observing this series limit, we can say whether the volume is high or low.

We can observe the spectral lines or series from the spectroscope in a hydrogen atom known as Hydrogen Spectrum Series. The Spectrum series can be observed in several different ways at different stages of the hydrogen atom spectrum. So we have different classifications in the hydrogen Spectrum series. They are -

### Rydberg Formula

As we know that the hydrogen spectrum is an emission spectrum, the atoms get excited and transition to different energy levels. Niels Bohr can study these transitions. Again he gave a formula known as the Rydberg formula to calculate the wavelength of these spectral lines.

1/λ = RZ2(1/n12− 1/n2h).

Where,

Z is the atomic number

NL is the lower energy level

NH is the higher energy level

𝜆  is the wavelength

R  is the Rydberg constant has the value 1.09737✕107 m⁻¹

### Lyman Series

The Lyman Series can be stated as an advance or enhancement of Bohr's model. It was discovered during the 19th century by a scientist called alignment. It was named after him. According to Lyman, the atom transitions can take place from higher energy levels to energy level 1. That is n1 equal to 1. We can understand by observing the values of different wavelengths at each energy level.

 Energy Level (n) Wavelength (𝜆 in nm) in Vacuum ∞ 91.175 5 94.974 4 97.256 3 102.57 2 121.57

### Balmer Series (n1=2)

The series of spectral lines can be discovered by a scientist Balmer in the year 1882. It is also similar to that of the Lyman series. But the variation occurs in the level of energy. The lineman observes spectral series at energy level 1 whereas the Balmer observed spectral series at energy level 2. That means the transitions of atoms occur from higher energy levels to the second energy level.

### Paschen Series

German physicist Friedrich Paschen discovers this series of spectrum lines in the hydrogen Spectrum series in the year 1902. All these series were named after the scientist. This series also explains spectral lines' nature when the transitions took place from higher energy levels to the third energy level.

From this level of series, all the subsequent levels may overlap with this series.

### Brackett Series

This series of spectral lines can be observed in the year 1922 Friedrich Sumner Brackett. When electrons transition from higher energy levels to the 4th energy level, the Spectrum series is called the Brackett Series.

### Pfund Series

The series, which August Harman Pfund observed in 1924, is known as beef and cereals named after him. He observed that the series of spectral lines might appear when electrons' transitions take place from higher energy levels to the fifth energy level.

### Humphreys Series

American Physicist Curtis J Humphreys, in 1953, has displayed a spectrum of series where the electron transition takes place from higher energy states to 6th energy states.

Still, several series are discovered, but they are unnamed. As the research and studies are increasing, several inventions and discoveries can come to the spotlight.

1. Mention Various Series of the Spectrum and Different Parts of the Spectrum Where the Lines Fall.

Ans. Below are the various series of the spectrum and different parts of the spectrum where the lines fall -

• Lyman Series - ultraviolet band.

• Balmer series - H alpha line

• Paschen Series - infrared region

• Brackett Series - infrared region and forms an electromagnetic spectrum.

• Pfund series - infrared region

• Humphreys series- infrared region.

2. How Many Spectral Lines are There?

Ans. Spectral lines are the lines that are observed when the electron transitions take place from higher energy levels to lower energy levels. The two types of spectral lines are as follows -

• Emission lines: The emission lines are a category of spectral lines that may appear with discrete colours and having the background of black. These lines can be observed only when the particles emit the wavelength.

• Absorption lines: The other classification of spectral lines is absorption lines. These may appear in the form of dark colour bands with the same black background. These lines appear when the particles absorb the wavelengths.

3. How Many Spectral Lines Can be Observed in the Spectrum?

Ans. The spiritual lines can be observed when transitions take place from higher energy levels to lower energy levels. After several studies, generalizing the concept of several spectral lines has been concluded. The fourth energy level elements transition to the third level, and then two second-level further moves on to the first level.