Procedure for performing the real lab:
To find the refractive index of the glass plate:
- Align the laser source and the interferometer as described in the procedure to find the wavelength of the laser source.
- Place the rotation stage perpendicular to the optical path, between the beam splitter and the movable mirror.
- Mount the glass plate on the rotation stage, aligned perpendicular to the optical path. When the glass plate is introduced, the fringes will be shifted and will become blurred.
- Make the fringes sharp again by moving the mirror mount with the micrometer.
- Rotate the rotation stage slowly and count the number of fringe shifts that occur as the table rotates from perpendicular (0°) to an angle θ. The refractive index of the glass slide can be calculated using equation (3) on the theory page.
Procedure for performing the simulator:
- Using the combo box Choose laser, select the desired laser source.
- Switch ON the laser source using Power On button.
- A blurred fringe pattern will appear on the screen, shown in the zoomed view at the upper right corner of the simulator. Make the fringes sharp using the slider Adjust Mirror. Once a coarse adjustment has been made with the slider, the right and left arrow keys on the keyboard provide fine control of this adjustment.
- To find the refractive index of a glass plate, insert the glass plate in the laser beam using the button Place glass plate.
- Change the angle of incidence of light on the glass plate using the Angle of rotation slider. Note the number of fringes displaced. The refractive index n of the glass plate can be calculated using equation (3) from the theory page. Right and left arrow keys provide fine control.
- The thickness t of the glass plate can be changed using the Thickness of glass plate slider.
- The Reset button resets the whole experimental arrangement to its default (starting) configuration.
- The Show results button displays the results after doing the experiment.
- The experiment can be repeated for different laser sources and for glass plates of different thickness.
Observations and calculations:
Least Count = ..... cm
Calibration constant of the apparatus= .....
No: of fringes, N =.....
Distance moved for N fringes, d =...... cm.
Refractive index of the given glass plate = ........