An opaque warning plate is inside a sealed chamber. The plate has a red symbol on a white background.
A lamp inside the chamber shines directly onto the plate. An observer outside the chamber views the plate through a window that acts as a blue colour filter. The window is between the plate and the observer.
The table shows the visible wavelengths emitted by the lamp at each setting.
| Lamp setting | Visible wavelengths emitted |
|---|---|
| A | red and blue |
| B | red only |
The lamp is at setting A.
Explain why the red symbol appears very dark and the white background appears blue when viewed through the window.
The lamp is changed to setting B.
Explain how the appearance of the white background changes when it is viewed through the window.
93 exam-style questions on Edexcel GCSE Physics 5.1 Reflection, refraction and lenses, covering 5.1.1 Reflection, refraction and total internal reflection, 5.1.2 Specular and diffuse reflection, 5.1.3 Colour of light: absorption and filters, 5.1.4 Lenses: power, focal length and shape, 5.1.5 Ray diagrams for converging and diverging lenses, and 5.1.6 Real and virtual images. Each one has a worked solution and a mark scheme showing where the marks go.