Zeeman effect using Fabry-Perot Etalon bsc 4th year right now

Experiment No. 1

Title: Determination of e/m of an electron by normal Zeeman effect using Fabry-Perot Etalon

Aim:

To determine the charge-to-mass ratio (e/m) of the electron by studying the splitting of spectral lines under a magnetic field using the normal Zeeman effect and Fabry-Perot Etalon.

Apparatus Required:

• Fabry-Perot Etalon

• Spectrometer

• Electromagnet with regulated power supply

• Sodium vapor lamp

• High-resolution CCD camera or eyepiece

• Gauss meter (to measure magnetic field)

• Slit and collimator assembly

Theory:

The Zeeman effect refers to the splitting of spectral lines of atoms when placed in a strong magnetic field. In the normal Zeeman effect, a spectral line splits into three components — one unshifted (π) and two symmetrically shifted (σ+ and σ−). The shift in wavelength is related to the magnetic field B and used to determine the e/m of the electron.

The relation used is:

 

$$\Delta \lambda = \frac{e \lambda^2 B}{4\pi m c}$$

​

Where:

• $\Delta \lambda$ = wavelength shift

• $e/m$ = charge-to-mass ratio of electron

• $\lambda$= central wavelength of spectral line

• $B$= magnetic field strength

• $c$= speed of light

Diagram (Descriptive):

(Since images can’t be shown here, describe like this in the notebook)

• A sodium lamp is placed between the poles of an electromagnet.

• Light passes through the Fabry-Perot Etalon and enters the spectrometer.

• The interference rings are observed through an eyepiece or CCD.

• Magnetic field is measured using a Gauss meter across the poles.

Procedure:

1. Arrange the experimental setup with the sodium lamp placed in between the poles of the electromagnet.

2. Connect the Fabry-Perot Etalon and align the spectrometer for clear visibility of fringes.

3. Calibrate the system using zero magnetic field — observe and record the central fringe.

4. Gradually increase magnetic field and observe the splitting of interference fringes.

5. Use the Gauss meter to measure the magnetic field at each step.

6. Measure the fringe shift (∆r) in the Fabry-Perot ring pattern.

7. Repeat the experiment for different values of magnetic field.

8. Use the fringe shift and known constants to calculate e/m.

Observation Table: