This is the third of three ILSs about light. In this ILS the HTML5 Phet lab “Bending light - Prisms” is used. The same female avatar as in the previous ILSs about the Colour of light and Refraction 1 guides the students during the ILS. In the first part students are stimulated to think about the conditions under which we can see a rainbow. Furthermore a reference is made to the knowledge gained in the ILS “The colour of light” and in the ILS “Refraction of light 1”. After that two rounds of investigation are introduced. In the first one the students use a light ray with one colour which shines through a prism. In the second one they use white light. They will discover that the different colours in white light refract in a different way. At the end there is a video explaining how a rainbow exists and a quiz.