Physics Experiments in Undergraduate Labs

18 May 2022

Running physics experiments in your undergraduate lab that require changing wavelengths? Wouldn’t it be great to switch between these various wavelengths without the need to re-align the laser setup?

 

Undergraduate students conduct physics experiments as part of their learning. These experiments support students in progressing and developing their knowledge and understanding. Experiments are carried out in laboratories and will normally require lasers and other relevant physics equipment.

The use of lasers within learning environments is important to help students with their physics studies. This equipment is vital for students to learn first-hand, in a safe and suitable educational environment.

Photonics Technologies understands that conducting physics experiments can take time. So, we have developed a multi-wavelength laser, the HEXA-BEAM.

This wavelength-switching laser is versatile and designed to switch between up to 6 different wavelengths. All without changing the experiment setup, saving time and increasing control over the experiment. We’re confident that this laser will prove useful in every undergraduate University physics lab, up and down the UK.

 

HEXA-BEAM Laser

The HEXA-BEAM Laser has the ability to switch between different wavelengths by simply turning a knob. With one simple laser source, you can select your laser colour at the turn of a knob!

The HEXA-BEAM Laser offers the standard wavelengths of 405, 520, and 650 nm. Additional optional visible wavelengths are also available.  Please see more details about the HEXA-BEAM laser wavelengths.

 

Physics Experiments with the HEXA-BEAM Laser

18 May 2022

Physics experiment for rotating the plane of polarisation (also known as Biot’s sugar experiment)

Biot’s optical rotation experiment demonstrates the effect of chiral media (sugar solution) on the plane of polarisation of linearly polarised light. This experiment allows for investigation into the effects of polarisation, chirality, scattering, and fluorescence.

Chirality is the name given to the property of molecules and systems whose image cannot be superimposed upon its mirror image. When linearly polarised light is passed through a chiral medium, such as a sugar solution, the plane of polarisation of the incident light is rotated due to its asymmetric structure, creating bright and dark bands that can be observed along the optical path.

Linearly polarised light is composed of left and right circularly polarised partial light waves, with both components having equal amplitudes. When these partial waves propagate through the chiral material, they encounter different refractive indices due to the asymmetry of the medium. The partial wave that oscillates through a larger refractive index will travel slower than its counterpart, producing a phase difference between them. This phase difference causes the plane of polarisation to rotate. The angle of rotation caused by the differing refractive indices is described by the following equation:

Here, is the optical angle of rotation, and are the refractive indices of the left and right circularly polarised partial waves respectively, is the length of the optical path and is the wavelength of the light beam.

The rotation of linearly polarised light causes observable bright and dark bands to appear along the cell containing the solution because the light is not entirely observable from one angle.

Equipment required

  • HEXA-BEAM Laser

The HEXA-BEAM laser makes it easy to run this experiment in different colours, allowing for the student to appreciate the effect of wavelength on the experiment. With a knob at the back of the laser, students can quickly change wavelength without any realignment needed.

The HEXA-BEAM laser is aligned down the centre of the glass tube to reduce any scattering. The bands of minima/maxima are visible and their separation can be measured.

  • Glass tube
  • Rotatable polarising filter
  • Observation screen
  • Photon detector
  • Rule

Hexa beam laser experiment

Analysis

The specific rotation can be determined by the distance between successive minima or maxima, as the distance between these points is equivalent to a specific rotation of .  Therefore, the specific rotation of the polarisation plane can be calculated by adjusting the values in the below equation

where L is the distance between the consecutive extrema that are measured, and C is the concentration of the solution the laser is passing through. The values of the specific rotation can then be compared to a mathematical fit using Drude’s expression.

Sources of error

  • Inhomogeneity of solution – the presence of bubbles within the sugar solution will prevent accurate results being obtained
  • Location of the maxima/minima
  • Parallax error observing the maxima/minima due to the laser beam being contained within the glass tube
  • Position of detector outside glass tube
  • Scattering of laser beam entering the tube

Active vs Passive laser stability

21 November 2021

It is a daily task to ensure the laser beam points exactly to where it should be in your physics lab.  Active vs Passive laser stability is a key question that occupies researchers all the time.

Smart electronics is the answer!  We can stabilise your laser with specialised equipment which will ensure a controlled laser beam through a continuous feedback loop.

Dr Thomas Kinder explains how in the video below:

Laser beam stability

16 September 2021

Our Optical Mirror Mounts come in a variety of types and characteristics to deliver exceptionally high stability for laser beam and delivery:

  • Manufactured to exceptionally fine tolerances, providing a new benchmark for stability and precision with a fine- thread screws with a pitch of 170 TPI
  • Constructed from specially treated materials to prevent movements from mechanical stress and changing temperatures.

You can design your own configuration – chose from different front and back plates, adjusted screws, and colours!