Biopolis Dresden Imaging Platform

Contrasting Techniques

Brightfield

Theory

pdf

Polarization

Hands-on

Birefrigence

Concept demonstrated

Demonstrates the impact of materials with two different refractive indices.

 

Materials

  • calcite block
  • piece of paper with black dot on it

 

Practical Setup

  • if you have several calcite blocks, give each (group of) student one.
  • if you have only one calcite block, take an overhead projector to present
  • draw a black dot on a piece of paper and put the calcite block on top of it, then rotate it above the dot. What happens? Why?

 

 

Idea/Implementation

Peter Evennett

Polarization

Concept demonstrated

Demonstrates how polarizers block out light and what happens when birefrigent objects get inbetween.

 

Materials

  • a bigger, flat light source
  • two sheets of polarizers for each student (alternatively only one polarizer for each student and an already polarized light source (eg a computer screen))
  • gummibears
  • rulers
  • calcite blocks
  • other birefrigent objects

Practical Setup

  • each student can hold his/her polarizer(s) in front of the light source and rotate the polarizer(s). What happens?
  • then let them take a biregringent object and put it inbetween the polarizers ... observe what happens. Why?

 

Idea/Implementation

Peter Evennett, Humberto Ibarra Avila, Britta Schroth-Diez

Fluorescence Microscopy

Hands-on

Fluorescent Bottles

Concept demonstrated

Demonstrates the concept of fluorescence absorption and emission. 

 

Materials

  • clear plastic or glass bottles
  • laser pointers with different wavelengths
  • different solutions of fluorescent liquid. In our case: tonic water (quinine), solution of alexa fluor 488 carboxylic acid, solution of alexa fluor 633 carboxylic acid (eg. from Invitrogen)

Practical Setup

  • stand bottle with prepared solutions in a line in front of a white background
  • teacher shines (405 nm?) laser beam from the opposite side through the bottles
  • students observe the colours (ie. absorption and emission properties of the different solutions) by looking perpendicular onto the setup.

warning: do NOT point laser towards students!

Idea/Implementation

Ruth Hans

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