AQA GCSE Seeing Coloured Objects(Physics)
Seeing Coloured Objects
Before you attempt this section, make sure you review this page first!
You will need to understand the ideas of white light containing multiple colours along with how primary and secondary colours are formed.
Why does a red object appear red?
Red is a primary colour of light. So, one example of a primary colour (red) is shown below. For the other primary colours green and blue, see the table at the bottom of the page!
White light shines onto the red ball. The red ball will absorb all of the wavelengths of visible light except red. Any wavelengths that correspond to red light are reflected into the person’s eye. So, the person sees the ball as red.
Why does a magenta object appear magenta?
Magenta is a secondary colour of light, it is made up of red and blue light. Only one example of a secondary colour has been done here. For Yellow and cyan, see the summary table at the bottom of the page.
White light strikes the ball, all of the wavelengths of white light are absorbed except red and blue (magneta). The wavelengths due to red and blue (magenta) are reflected into the person’s eyes. So, the person sees the ball as magenta.
Why does a white ball appear white?
When white light shines onto a white object, none of the wavelengths of light are absorbed, they are all reflected. So, we see the object as white.
Why does a black ball appear black?
When white light shines onto a black ball, it will absorb all the wavelengths of visible light, so none of the light is reflected. We see the object as black.
| Colour of Object | Type of light shone onto the object | Wavelengths of light that the object absorbs | Wavelengths of light that the ball will reflect |
|---|---|---|---|
| Red | White | All, except Red | Red |
| Green | White | All, except Green | Green |
| Blue | White | All, except Blue | Blue |
| White | White | None | White |
| Black | White | All | None |
| Magnenta | White | All, except Magnenta(red and blue) | Magenta (Red and blue) |
| Yellow | White | All, except Yellow(red and green) | Yellow (red and green) |
| Cyan | White | All, except Cyan (blue and green) | Cyan (blue and green) |
Practice Question
1.Write down the names of primary light colours which make up white light
2. Write down the names of the secondary light colours which make up white light
3. A red beam of light is mixed with a Cyan beam of light. What colour light is produced?
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Drawing ray diagrams for a concave lens
Drawing Ray Diagram to produce a virtual image for a convex lens
Drawing ray diagram to produce a real image for a convex lens.
Specular and Diffuse Reflection
Seeing Coloured Objects Part 2
Viewing objects through coloured filters
Transparent, Translucent and Opaque