Why objects look coloured, what opaque, transparent and translucent mean, and what filters and coloured lights do.
What you will learn
- Explain the colour of an opaque object in white light
- Predict the colour of an object in coloured light or behind a filter
- Find the frequency of a colour from its wavelength
Each colour is a band of wavelengths
Visible light runs from red (wavelength about 700 nm) through orange, yellow, green and blue to violet (about 400 nm).
Each colour is a narrow band of wavelengths, so also a narrow band of frequencies. White light is a mixture of all of them.
wave speed = frequency × wavelength
v = f λ (AQA and Edexcel: recall)
- Green light, λ = 530 nm, speed 3.00 × 10⁸ m/s
- 530 nm = 5.30 × 10⁻⁷ m
- f = 3.00 × 10⁸ ÷ 5.30 × 10⁻⁷ = 5.66 × 10¹⁴ Hz
The rest of this lesson and its 9 practice questions are locked.
In this lesson
- Each colour is a band of wavelengths
- Reflect, absorb or transmit
- Filters and coloured light
- Try it: Coloured objects in coloured light
9 practice questions, marked as you go; about 20 minutes in all.
Key terms
Opaque, White, Black, Transparent, Translucent, Filter
In this unit: Lenses, visible light, sound and black bodies
Reflection and the glass block practical, total internal reflection and optical fibres, colour and filters, lenses and magnification, sound and echoes, ultrasound and seismic waves, and black body radiation (Physics only).