Authors: Ing. Wolfgang Laube, Prof. Dr. Philipp Weihs
Basic Idea of the Building Block
The following experiment illustrates direct solar radiation focused on one point using a Fresnel lens. A test tube is filled with water and positioned at the focal point. Inside the test tube is a black (absorbing) area (on the side of the tube positioned away from the sun) that converts the sun’s energy into heat. The majority of this heat is transferred into the water. The water is brought to a boil. Using the test tube’s built-in thermal element it is possible to observe changes in the water as it heats up.
This experiment should help students understand the energetic significance of the sun.
Description of the building block
This experiment must be carried out when the sun is shining in order for it to be successful.
A test tube with a specially made fixture is filled with water. A (focusing) Fresnel lens is aligned with the sun. It should be focused exactly on the lower part of the test tube.
The water is brought to a boil. Using the pre-measured amount of water (by weight) and the water temperature, the energy expended to boil the water can be calculated.
The building block is divided into four steps:
Step 1: Directions for the experiment/ technical description
Step 2: Experiment preparations
Step 3: Experiment execution
Step 4: Calculating the expended amount of energy
Course material include
- A short introduction to the building block
- A video ( )
- A short theoretical explanation
- Bibliography and further links