Starter quiz
- In a ______ wave, the oscillations are perpendicular (at right angles) to the direction of wave travel.
- 'transverse' ✓
- Most waves happen by oscillations of particles in a substance. Which of the following words is used to describe any substance that a wave travels through?
- oscilloscope
- prism
- medium ✓
- trough
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- A sound wave has frequency 12 Hz. Which of the following statements explains what a frequency of 12 Hz means?
- The wave is 12 cm high.
- There are 12 wavelengths per metre.
- There are 12 wavelengths per centimetre.
- 12 wavelengths pass by a point every hour.
- 12 wavelengths pass by a point every second. ✓
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- Which of the following is a correct arrangement of the wave equation?
- ✓
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-
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- When a wave crosses a boundary from one medium to another, it …
- never changes direction.
- always changes direction.
- changes direction if it is travelling perpendicular to the boundary.
- changes direction if it is not travelling perpendicular to the boundary. ✓
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- When a light ray travels from air to glass (and is not moving at right angles to the boundary), the ray bends …
- towards the normal. ✓
- away from the normal.
- parallel to the normal.
- perpendicular to the normal.
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Exit quiz
- What are electromagnetic waves?
- oscillations of air molecules
- oscillations in electric and magnetic fields ✓
- high speed sound waves
- high speed ultrasound waves
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- Which of the following colours of light has the lowest frequency?
- blue
- green
- red ✓
- violet
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White light is split into its separate colours by this triangular prism. This is because some frequencies are ______ more than others.- absorbed
- dispersed
- reflected
- refracted ✓
- transmitted
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- Which of the following statements are true for an opaque blue object?
- It reflects red light.
- It absorbs red light. ✓
- It reflects blue light. ✓
- It absorbs blue light.
- It transmits blue light.
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- A student shines pure red light and pure green light onto a white piece of paper. Which of the following statements are correct?
- The light makes the white paper look brown.
- The light makes the white paper look yellow. ✓
- If pure blue light is also shone onto the paper, the paper will look black.
- If pure blue light is also shone onto the paper, the paper will look white. ✓
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- Which of the following primary colours of light are transmitted by a cyan filter?
- none of them
- blue only
- blue and green only ✓
- blue and red only
- red and green only
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- The different colours of light are electromagnetic waves with different frequencies and wavelengths.
- A triangular prism can produce a colour spectrum from white light, showing it is a mixture of all visible wavelengths.
- From red to violet in the spectrum, frequency increases and wavelength decreases. Higher frequencies refract further.
- Opaque objects transmit no incident light. Their colour depends on which wavelengths of incident light are reflected.
- Colour filters only transmit some wavelengths. The filter colour depends on the transmitted wavelengths.
Common misconception
Pupils assume that the colours of light will mix in the same way that paints mix.
Make it explicit in your teaching that the primary colours of light (red, green and blue) are different, and mix differently, to the primary colours of paint that pupils may have been taught elsewhere (e.g. red, yellow and blue).
Keywords
Electromagnetic wave - Electromagnetic waves are ripples/oscillations in the invisible electric and magnetic fields that are all around us.
Frequency - The frequency of a wave is the number of oscillations that occur per second.
Wavelength - The wavelength of a wave is the distance between one point on a wave and the same point on the next wave.
Refract - Waves are said to refract when they change direction upon entering a new medium.
Opaque - An object is opaque if no light is transmitted through it.