OCR · A-Level · Physics
Course version: H556 · Version from Sept 2015
(a) electromagnetic spectrum; properties of electromagnetic waves
Full specification wording
Electromagnetic waves: (a) electromagnetic spectrum; properties of electromagnetic waves
The electromagnetic spectrum is the continuous family of transverse waves that propagate through a vacuum at the speed of light, c = 3.00 × 10⁸ m s⁻¹.
Checked against the OCR H556 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The electromagnetic spectrum is the continuous family of transverse waves that propagate through a vacuum at the speed of light, c = 3.00 × 10⁸ m s⁻¹. Its regions, in order of increasing frequency and decreasing wavelength, are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. All electromagnetic waves share key properties: they are transverse, can travel through a vacuum, transfer energy, and show reflection, refraction, diffraction, interference and polarisation. They differ in wavelength, frequency, photon energy and typical interaction with matter.
What earns the marks
- Electromagnetic waves are transverse oscillations of electric and magnetic fields and do not require a medium.
- All regions travel through a vacuum at c = 3.00 × 10⁸ m s⁻¹.
- The spectrum order from longest to shortest wavelength is radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
- Frequency and wavelength are inversely related through c = fλ, so increasing frequency means decreasing wavelength.
- All regions can be reflected, refracted, diffracted, interfere and be polarised.
- Regions differ in photon energy E = hf and in how they interact with matter.
Common mistakes and how to put them right
Thinking electromagnetic waves need a medium.
Put it right: They propagate through a vacuum, unlike sound.
Believing visible light is the only region that can be polarised.
Put it right: All electromagnetic waves can be polarised.
Reversing the spectrum order.
Put it right: Radio waves have the longest wavelength and gamma rays the shortest.
Assuming all regions have the same photon energy.
Put it right: Energy depends on frequency, so gamma photons carry far more energy than radio photons.
Exam tips
- Learn the spectrum order as a sequence and check whether the question asks for increasing frequency or increasing wavelength.
- Use c = fλ to convert between wavelength and frequency rather than memorising separate values.
- Eliminate options that claim electromagnetic waves are longitudinal or need a medium.
- Check units and powers of ten carefully when comparing wavelengths.
Try the lesson
The start of the Electromagnetic waves: (a) electromagnetic spectrum; properties of electromagnetic waves lesson, made from checked teaching notes for this specification point.
Listen
The electromagnetic spectrum is the continuous family of transverse waves that propagate through a vacuum at the speed of light, c = 3.00 × 10⁸ m s⁻¹. Its regions, in order of increasing frequency and decreasing wavelength, are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. All electromagnetic waves share key properties: they are transverse, can travel through a vacuum, transfer energy, and show reflection, refraction, diffraction, interference and polarisation. They differ in wavelength, frequency, photon energy and typical interaction with matter. A strong answer earns marks for these points. Electromagnetic waves are transverse oscillations of electric and magnetic fields and do not require a medium. All regions travel through a vacuum at c = 3.00 × 10⁸ m s⁻¹. The spectrum order from longest to shortest wavelength is radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Frequency and wavelength are inversely related through c = fλ, so increasing frequency means decreasing wavelength. Exam tip: Learn the spectrum order as a sequence and check whether the question asks for increasing frequency or increasing wavelength.
See it
Put it in order
Put these steps in the order they happen.
- 1. Gamma rays
- 2. X-rays
- 3. Infrared
- 4. Ultraviolet
- 5. Radio waves
- 6. Microwaves
- 7. Visible light
Key words
Say what each word means before you turn the card.
Transverse wave nature
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Propagation through vacuum at c
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Spectrum ordering by wavelength and frequency
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Shared wave behaviours and differing photon energies
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See every definition
- Transverse wave nature
- Electromagnetic waves are transverse oscillations of electric and magnetic fields and do not require a medium.
- Propagation through vacuum at c
- All regions travel through a vacuum at c = 3.00 × 10⁸ m s⁻¹.
- Spectrum ordering by wavelength and frequency
- The spectrum order from longest to shortest wavelength is radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
- Shared wave behaviours and differing photon energies
- All regions can be reflected, refracted, diffracted, interfere and be polarised, while regions differ in photon energy E = hf and in how they interact with matter.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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