2. NEWTON’S EXPERIMENT
We used a head light (with a narrow slit)
A shine a ray of white light through a glass
prism and on to a white screen
We could see the seven colours of the
spectrum
4. How does a prism disperse white
light into a spectrum?
• Different colours of light have different wavelengths.
• All colours of light travel at the same speed in a vacuum. When they enter a
transparent substance like glass, they all slow down but by different amounts.
• Because they slow down by different amounts, different colours are refracted
through different angles.
• For example:
1. Violet: have the shortest wavelength, is refracted through the largest angle.
2. Red: have a longer wavelength, is deviated through a smaller angle.
5. The electromagnetic spectrum
Properties of all electromagnetic waves:
1. They transfer energy from one place to another.
2. They are all transverse waves.
3. They can all be reflected, refracted, diffracted.
4. They can all travel through a vacuum (space).
5. They all travel at 300 000 000 m/s in a vacuum.
6. Wave speed = frequency x wavelength.
7. The shorter the wavelength (the higher the frequency), the more dangerous they are.
6. Subtraction of colour 1
What happens when white light shines on coloured objects?
Blue objects absorb ROYGV and leave B to be reflected to our
eyes. Red leave R reflected.
Black objects absorb all the colours and white absorb none.
7. Subtraction of colour 2
Some experiments. We put FILTERS in front of a white light.
WITHOUT FILTERS
RED FILTER GREEN FILTER RED AND GREEN
FILTERS
ALL THE FILTERS
8. Subtraction of colour 3
More experiments, we looked at coloured objects in coloured lights.
Our results were:
COLOUR
OBJECT
FILTERED LIGHT APPEARANCE
White Red Red
Blue Red Light red/violet
White Yellow Yellow
Blue Yellow Light yellow
Pictures of the experiments:
In practice most filters are not
perfect
9. Addition of colour
We did an experiment. We had green, blue
and red lights. And we made some
variations. For example, we put together two
different filters or all of them together.
BLUE + RED GREEN + RED BLUE + GREEN
