Waves, the spectrum and their uses
All waves transfer energy without transferring matter. One equation and one classification cover most of the topic.
Lesson overview
What you'll learn in this lesson
Apply the laws of motion and wave behaviour to explain and calculate.
Key learning points
- • Describing waves
- • The electromagnetic spectrum
- • Behaviour and hazards
This lesson at a glance
- 30 minutes
- 15 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 15
Watch first
Waves, the spectrum and their uses
An English teaching video on this topic from Cognito. Watch it, then scroll down for the lesson.
In a nutshell
Apply the laws of motion and wave behaviour to explain and calculate.
Learning cycle
Part 2 of 15
Learning cycle 1 of 2
Part 1 · Describing waves
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 15
Learn
Describing waves
Amplitude is the maximum displacement from rest, wavelength the distance between corresponding points and frequency the number of waves per second in hertz. The wave equation v = fλ links them. In transverse waves the oscillation is perpendicular to the direction of travel; in longitudinal waves, such as sound, it is parallel.
Explore the idea
Part 4 of 15
Learn
The electromagnetic spectrum
Radio, microwave, infrared, visible, ultraviolet, X-ray and gamma, in order of increasing frequency and decreasing wavelength. All travel at the same speed in a vacuum. Uses follow properties: microwaves for communication and heating, infrared for thermal imaging, X-rays for medical imaging, gamma for sterilisation.
Quick check
Part 5 of 15
Quick check
The wave equation is
Quick check
Part 6 of 15
Quick check
Sound is a
Reset break
Part 7 of 15
Pause
That's sitting 1 of 2 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 8 of 15
Learning cycle 2 of 2
Part 2 · Behaviour and hazards
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 9 of 15
Learn
Behaviour and hazards
Waves reflect, refract when they change speed entering a new medium, and can be absorbed or transmitted. Higher-frequency radiation carries more energy, so ultraviolet can damage skin cells and X-rays and gamma rays can cause mutations, which is why exposure is controlled and shielding is used.
Quick check
Part 10 of 15
Quick check
Which has the highest frequency?
Quick check
Part 11 of 15
Quick check
Refraction happens because a wave
Explore the idea
Part 12 of 15
Worked example
Worked answer: a wave has frequency 50 Hz and wavelength 6 m. Find its speed (3 marks)
The wave equation is v = fλ (1). Substituting: v = 50 × 6 (1) = 300 m/s (1). Rearranging, a wave of the same speed with double the frequency would have half the wavelength, since speed is fixed by the medium the wave travels through.
Challenge round
Part 13 of 15
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Mastery quiz
Part 14 of 15
Marked quiz
End of lesson quiz: Waves, the spectrum and their uses
4 questions, marked with the reasoning shown. No timer.
1. The wave equation is
2. Sound is a
3. Which has the highest frequency?
4. Refraction happens because a wave
Lesson round-up
Part 15 of 15
Lesson round-up
Ready when you are
Quiz score
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Points this lesson
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Best run
0 in a row
Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo the work
Your written work for this lesson
This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.
Why the school greenhouse failed
A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.
The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.
The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.
Written for Good Learning Co.
Reading questions
- Name the variable the club changed the second time, and one variable they kept the same.
- Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
- Write a conclusion for the club's report, saying how far the evidence supports it.
Method and results
WritingWrite the aim, what you changed, what you measured and what you kept the same, then record your results in a table.
1 page + results table
Conclusion
WritingExplain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.
6–8 sentences
Labelled diagram
DiagramDraw the apparatus or the process in pencil, label it fully, and photograph it.
1 labelled diagram
Reading and notes
ReadingRead the lesson text again and write the key ideas in your own words.
Half a page of notes
Saved as you type.
Part 1 of 15 · Watch & discover