Rainbows

Rainbows

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Rainbows

Language: English
Description: The rainbow is a good starting point when discussing properties of light. The students investigate the influence of prisms and other transparent objects when passed by light beams. A rainbow can be modelled by letting white light refract in a transparent circle, representing a raindrop.
Target: Key Stage 2
Category: Demonstration, Exercise
Discipline: Optics
Learning objectives:

Understand that white light is a mix of all colours (wavelengths). Know the colours of the rainbow.

In class: Start with discussing the rainbow.

How and when does a rainbow appear? Where does the light come from? Where do the colours come from?

Let the students come up with suggestions. Discuss how white light can split up into rainbow colours. Discuss other phenomena when rainbow colours appear. Demonstrate how a prisms refracts white light.

Discuss how this can be visualized and explored in Algodoo. Let the students create scenes in Algodoo using the suggestions you came up with together or let them use their own ideas. Help the students make decisions and ask guiding questions. Encourage the students to follow the procedure Create – Predict – Interact – Evaluate.

Allow the students to follow-up and share their experiences in class after the simulation.

Steps in Algodoo


Create a scene

Create a prism by using the polygon tool and setting material to glass.
Prism.png


Make a prediction

What happens when white light hit the prism? Is the light white all the way through the prism? What happens when the color of the laser beam is changed? Do all colors behave the same?


Run/Interact

Let a white light beam shine at the prism. Create white light by decreasing Saturation. Rotate the prism, move the light beam to watch the effects.


Evaluate

Add more glass objects after the prism and investigate what happens with the scattered light from the prism. How do the different colors behave? Do they refract in the same way?


Revise scene

Model a raindrop by creating a transparent circle with refraction index 1.3.
Rainbow.png


Make a prediction

What happens with a white light beam when it hits the raindrop?


Run/Interact

Let a white laser represent the sun and let the beam hit the raindrop. Rotate laser or move it up and down to alter the angle of incidence. What happens with the intensity of the refracted light?


Evaluate

Which refracted beam is actually the rainbow? What happens with the light that goes out on the other side of the rainbow?
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