Diffraction and

Optical bench to qualitatively and quantitatively study phenomena of diffraction and interference

A laser beam is directed onto a revolving base where slits, holes and other openings are made. The resulting diffraction patterns are received by a light sensor, which is linked to the linear position sensor. If we move horizontally the sensor we obtain a voltage proportional to the light intensity associated to the sensor position. If we connect the outputs of the two sensors to a data acquisition system we will then obtain, in real time, the curves that indicate how light intensity varies according to the position. As we know the geometrical characteristics of the slits and their distance from the light sensor, we will also be able to quantitatively assess these phenomena.

Experiments that can be performed:

  • diffraction phenomena;
  • interference phenomena ;
  • polarization phenomena;
  • verification of Malus's law.

Optical bench to study phenomena of polarization

The optical bench can also be fitted with a pair of aligned linear polarizers to be assembled on the apposite base. One of these polarizers can be manually rotated by means of a handle and is also connected to an angular position sensor.

This allows us to obtain a curve indicating the luminous intensity of light produced in relation to the angle formed by the two polarizers.


Material supplied as standard:
  • optical bench
  • light sensor
  • linear position sensor
  • high-quality diode laser
  • power supply unit for laser diode with variable intensity
  • supports
  • screens
  • 2 sets of revolver slits
  • cables
Module for experiments on polarization :
  • angular position sensor
  • 2 linear polarizers

The  graph of figure 1 was obtained by pointing the laser beam at a slit with a width  a = 0.04 mm located at a distance  L = 700 mm from the sensor.

As we know that the laser wavelength is λ=635 nm, we will be able to assess the relation that provides the distances of minimums from the central point

 X m=Lnλ / a     for n = 1,2,3,...

Moreover we can, for instance, measure the ratio between the intensity of the first secondary maximum and that of the central maximum.

The  graph of figure 2 was drawn by pointing the laser beam at a double slit. It clearly shows the superposition of two undulatory phenomena: the interference according to Young produced by the two slits and the diffraction generated by every single slit.
Additional components available separalely:

Didactical material:
  • Student guide to experiments
  • Teacher manual