Absorption and Emission Spectra

EMISSION SPECTRA

What process creates the lines on an emission spectra?

The de-excitation of electrons

Describe how this process allows the formation of an emission spectra

(With steps on how to calculate)

When electrons de-excite they release a photon. By calculating the wavelength of this photon we can determine where it will be placed on a spectrum.

STEP’s:

1- hf=E1-E2, find the difference in energy levels

2- Convert this energy from MeV to J

3- E=hf, Find the frequency

4- C=f lander, Calculate the wavelength

Describe the appearance of an emission spectra

Discrete wavelengths represented by colourful lines on a black background

What produces emission spectra?

Hot, low-pressure gases, such as a nebula surrounding a star

ABSORPTION SPECTRA

When does an absorption line appear on a spectrum?

When an absorbing material is placed between the source and the observer

What process produces an absorption spectrum?

The absorption of a photon by an electron causing it to excite

Describe the appearance of an absorption spectrum

Discrete wavelengths represented by black lines on a continuous spectrum

What produces an absorption spectrum?

Cool, low-pressure gases, such as the photosphere of a star

What is a similarity between the absorption and emission spectrums?

For the same element, the lines on an emission spectrum correspond to the line on an absorption spectrum

What are the differences between the absorption and emission spectrums?

(3 points)

1- Absorption is a result of the excitation of electrons, whereas emission is a result of the de-excitation of electrons

2-The lines on an absorption spectrum demonstrate discrete wavelengths over a continuous spectrum, the discrete wavelengths of the emission spectrum are represented by colourful lines over a black background

3-Absorption is produced by cool, low-pressure gases, whereas emission is produced by hot, low-pressure gases

What do the lines on both spectrums allow us to do?

They allow us to identify specific elements, such as the ones in stars

What are the 3 types of spectra?

1- Continuous emission spectra

2- Emission line spectra

3- Absorption line spectra