OCR · GCSE · Physics
Course version: J249 · Version from Sept 2018
Describe the main groupings of the electromagnetic spectrum and that these…
Full specification wording
The electromagnetic spectrum: describe the main groupings of the electromagnetic spectrum and that these groupings range from long to short wavelengths and from low to high frequencies (to include: radio, microwave, infrared, visible (red to violet), ultraviolet, X-rays and gamma rays)
The electromagnetic spectrum is one family of transverse waves that all travel at the same speed in a vacuum, about 3.0 × 10⁸ m/s.
Checked against the OCR J249 specification (opens in a new tab) on .
- Point 4 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The electromagnetic spectrum is one family of transverse waves that all travel at the same speed in a vacuum, about 3.0 × 10⁸ m/s. Its groupings, in order of decreasing wavelength and increasing frequency, are radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays. Within the visible band, red has the longest wavelength and lowest frequency, while violet has the shortest wavelength and highest frequency. Because speed equals frequency multiplied by wavelength, a wave with a longer wavelength must have a lower frequency when the speed is fixed. A useful check is to place the seven groupings in a line and confirm that moving right shortens the wavelength and raises the frequency.
What earns the marks
- Places radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays in the correct order from longest to shortest wavelength.
- States that the groupings range from long to short wavelengths and from low to high frequencies.
- Identifies red as the long-wavelength, low-frequency end of the visible band and violet as the short-wavelength, high-frequency end.
- Uses the fixed speed of electromagnetic waves to link a longer wavelength with a lower frequency.
Common mistakes and how to put them right
Reverses the order so that gamma rays are placed at the long-wavelength end.
Put it right by listing radio first and gamma rays last.
Treats frequency and wavelength as increasing together.
Put it right by noting that at fixed speed a longer wavelength means a lower frequency.
Places violet before red within the visible band.
Put it right by putting red at the long-wavelength end and violet at the short-wavelength end.
Exam tips
- Learn the seven groupings as an ordered list and rehearse it in both directions.
- Check any answer by asking whether wavelength falls and frequency rises as you move along the list.
- For visible light, anchor red as long wavelength and violet as short wavelength before answering.
Try the lesson
The start of the The electromagnetic spectrum: describe the main groupings of the electromagnetic spectrum and that these groupings range from long to short wavelengths and from low to high frequencies (to include: radio, microwave, infrared, visible (red to violet), ultraviolet, X-rays and gamma rays) lesson, made from checked teaching notes for this specification point.
Have a go first
Which grouping of the electromagnetic spectrum has the highest frequency?
Listen
The electromagnetic spectrum is one family of transverse waves that all travel at the same speed in a vacuum, about 3.0 × 10⁸ m/s. Its groupings, in order of decreasing wavelength and increasing frequency, are radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays. Within the visible band, red has the longest wavelength and lowest frequency, while violet has the shortest wavelength and highest frequency. Because speed equals frequency multiplied by wavelength, a wave with a longer wavelength must have a lower frequency when the speed is fixed. A useful check is to place the seven groupings in a line and confirm that moving right shortens the wavelength and raises the frequency. A strong answer earns marks for these points. Places radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays in the correct order from longest to shortest wavelength. States that the groupings range from long to short wavelengths and from low to high frequencies. Identifies red as the long-wavelength, low-frequency end of the visible band and violet as the short-wavelength, high-frequency end. Uses the fixed speed of electromagnetic waves to link a longer wavelength with a lower frequency. A common slip: Reverses the order so that gamma rays are placed at the long-wavelength end. Instead, listing radio first and gamma rays last. Exam tip: Learn the seven groupings as an ordered list and rehearse it in both directions.
See it
Key words
Say what each word means before you turn the card.
Order of the electromagnetic groupings
Try answering aloud or in your head before turning the card.
Wavelength and frequency relationship
Try answering aloud or in your head before turning the card.
Position of colours within visible light
Try answering aloud or in your head before turning the card.
Fixed speed of electromagnetic waves
Try answering aloud or in your head before turning the card.
See every definition
- Order of the electromagnetic groupings
- The groupings, in order of decreasing wavelength and increasing frequency, are radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays.
- Wavelength and frequency relationship
- Because speed equals frequency multiplied by wavelength, a wave with a longer wavelength must have a lower frequency when the speed is fixed.
- Position of colours within visible light
- Within the visible band, red has the longest wavelength and lowest frequency, while violet has the shortest wavelength and highest frequency.
- Fixed speed of electromagnetic waves
- The electromagnetic spectrum is one family of transverse waves that all travel at the same speed in a vacuum, about 3.0 × 10⁸ m/s.
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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