Lighting the slums of the Philippines
This YouTube video shows a household demonstration of the refraction of light.
The resource is a 6.25-minute video showing how the ability to refract light can be used to develop a simple cheap technology to solve problems.
In the slums of a neighbourhood in the Philippines, the houses are so close together that they get very little natural light. A Filipino man uses a recycled PET bottle filled with water and a little bleach to solve the problem.