Build your own spectrophotometer using LEGO!

Hypothesis

With regard to the principles of absorption spectroscopy, the Beer−Lambert law is derived by considering that the loss of light traversing an absorbing material is proportional to the amount of light present initially, −dI/dx ∝ I. This is shown directly using the first configuration of the experiment and also offers an opportunity to explain why exponential functions are so common in physical sciences.

Objectives

• Understand the principles of absorption spectroscopy, together with the concepts of absorbance and molar extinction coefficient.
• Provide a visual and quantitative validation of the Beer−Lambert law.
• Develop their scientific inquiry skills.
• Know the meaning of spectrophotometer, absorption spectrum, Beer-Lambert law concept.

Introduction

In this laboratory experience, students will gain basic knowledge on absorption spectroscopy with a simple, low-cost instrument using interlocking bricks and few optical components that can (with minimal changes) function as both a spectrophotometer and fluorometer. The spectrometer allows the collection of semiquantitative data, requiring both data analysis and calibration, as these are essential components of practical spectroscopy.