Physics Lesson 4b — Waves

Frequency & Period

Spec 3.1 · 3.3

⏱️🔢🔁📻📐

Learning Objectives:

3.1 – Use the units: hertz (Hz), second (s).
3.3 – Know the definitions of frequency and period, and the relationship T = 1/f.

🏆 By the end I will be able to…

All: define frequency and period, and name their units.

Most: use T = 1/f to calculate period from frequency (and back).

Some: explain why frequency and period are inversely related, with worked examples.

Navigation: Arrow Keys or Spacebar

🖨️ Pupil Packs

⏱️ 40-Minute Pacing Guide

Core path (40 min): Arrival → Starter → I Do → We Do → Independent → Exit Ticket

Part 2 of 3 — follows 4a Wave Anatomy, and leads into 4c Energy Transfer.

⏱️ 4 min

Arrival Task

Arrival Task – Recall from Last Lesson

Instructions: Answer from memory. Questions 1–3 recap 4a — question 4 previews today.

1. 🟢

What is the highest point of a wave called?

A) TroughB) CrestC) AmplitudeD) Wavelength

✅ B) Crest.

2. 🟢

What is amplitude?

A) How tall the wave isB) How fast it movesC) The colourD) The smell

✅ A) How tall the wave is.

3. 🟢

If something happens "frequently", it happens…

A) RarelyB) OftenC) NeverD) Slowly

✅ B) Often.

4. Lead-in 🔢

If 5 waves pass a point in 1 second, how many is that per second?

A) 1B) 5C) 10D) 0

✅ B) 5. That's a frequency of 5 per second.

1. 🟠

Define wavelength.

A) Height of the waveB) Distance from one wave to the nextC) The wave's speedD) The wave's colour

✅ B) Distance from one point on a wave to the same point on the next wave.

2. 🟠

What do you think "frequency" might measure?

A) How tall waves areB) How often waves happen each secondC) How wide waves areD) The wave's colour

✅ B) How often waves happen each second.

3. 🟠

If a clock ticks once per second, how many ticks happen in 5 seconds?

A) 1B) 5C) 10D) 0.5

✅ B) 5 ticks.

4. Lead-in 🔢

A "class period" is a length of time. What do you think "period" might mean for a wave?

A) The colour of a waveB) The time for one wave to passC) The height of a waveD) The number of waves

✅ B) The time for one wave to pass.

1. 🔵

What is a wavefront?

A) A single point on a waveB) A line joining points at the same stage of a waveC) The front of a boatD) The end of a wave

✅ B) A line joining points at the same stage of vibration.

2. 🔵

An event happens 10 times in 2 seconds. How many times per second?

A) 5B) 10C) 20D) 2

✅ A) 5 per second (10 ÷ 2).

3. 🔵

Event A happens every 0.5 s. Event B happens every 2 s. Which happens more often?

A) AB) BC) SameD) Can't tell

✅ A) A — a shorter gap between events means it happens more often.

4. Lead-in 🔢

If frequency tells you how many waves per second, what do you think "period" tells you?

A) How many waves in totalB) The time for ONE waveC) The colour of the waveD) The height of the wave

✅ B) The time for ONE wave to pass.

⏱️ 3 min

Starter

Starter: Units Match-Up 🔢

Instructions: In your book, match each quantity to its correct unit and symbol using the word bank. 3 minutes.

📝 Complete the Table

Quantity	Unit	Symbol
Frequency	?	?
Wavelength	?	?
Wave speed	?	?
Period	?	?

💡 Word bank: Hz (hertz) · m (metre) · m/s · s (second)

💡 Did You Know?

A hummingbird's wings beat about 50 times per second — that's a frequency of 50 Hz! Human ears can hear frequencies from about 20 Hz up to 20,000 Hz.

🌟 Think ahead: If frequency is "per second", what unit do you think would make sense for something measured "in seconds"? Have a guess before I Do.

⏱️ 6 min

I Do

I Do: Frequency & Period (3.3)

Key Idea: Frequency and period both describe how fast a wave repeats — and they're linked by one formula.

0 / 4 revealed

🔄 Frequency, Period & the Link

Frequency (f) — the number of complete waves passing a point per second. Measured in hertz (Hz).

Period (T) — the time taken for one complete wave to pass. Measured in seconds (s).

They're inverses of each other: T = 1 ÷ f f = 1 ÷ T

Example: if f = 5 Hz → each wave takes T = 1 ÷ 5 = 0.2 s. If T = 0.02 s → f = 1 ÷ 0.02 = 50 Hz.

Frequency vs Period

Quantity	Symbol	Unit
Frequency	f	Hz
Period	T	s

If they ask "what happens to the period when frequency increases?" — the answer is always: period decreases. They are inversely proportional.

Talk to your partner: If f = 10 Hz, what is T? Work it out together, then check with T = 1/f. Be ready to match some pairs yourself next.

⏱️ 6 min

We Do

We Do: Match Frequency to Period 🔢

Instructions: Click a frequency card on the left, then click the matching period card on the right. Use T = 1/f to work each one out. Get all 5!

👥 Think-Pair-Share: Try it yourself → discuss with your partner → agree on the answer.

Frequency (click first)

f = 2 Hz

f = 5 Hz

f = 10 Hz

f = 4 Hz

f = 20 Hz

Period (then click match)

T = 0.1 s

T = 0.5 s

T = 0.05 s

T = 0.2 s

T = 0.25 s

Matched: 0 / 5

🧡 Tip: T = 1 ÷ f. So f = 2 Hz gives T = 1 ÷ 2 = 0.5 s. Work through each card the same way.

f=2→T=0.5s · f=5→T=0.2s · f=10→T=0.1s · f=4→T=0.25s · f=20→T=0.05s

⏱️ 8 min

Independent Work

Instructions: Complete the tasks in your printed pack independently.

📝 Your Pack Contains:

Section A: Multiple Choice (4 questions)

Section B: Short Answer — calculate T and f

Section C: Long Answer — explain the relationship

Section D: Exam-Style Question

Need help? Check the Scaffolding Sheet for the formula and worked examples.

Exam Command Words:
State = write a fact, no explanation needed.
Calculate = show the formula, substitute, get the answer + unit.
Explain = say what happens AND why (use "because").
Describe = say what happens step by step (no "why" needed).

🏆 Success Criteria

Foundation (Grades U–1): I can define frequency and period, and name their units.

Middle (Grades 1–2): I can use T = 1/f to calculate period from frequency (and back).

Higher (Grades 3–5): I can explain why frequency and period are inversely related, with worked examples.

✅ Tick as you go — Success checklist

I can define frequency (Hz) and period (s)

I can use T = 1/f

I can use f = 1/T

I can explain why they're inversely related (Middle/Higher)

⏱️ 3 min

Exit Ticket

Exit Ticket – Check Your Learning

Instructions: Answer independently. No notes.

🟢 I'm confident — I could teach this

🟡 Getting there — need more practice

🔴 I'm stuck — I need help

🖨️ Print written exit ticket:

1) What is frequency the measure of?

The number of complete waves passing a point per second.

2) What unit is frequency measured in?

Hertz (Hz).

3) What unit is period measured in?

Seconds (s).

Name: ________________________ Class: __________ Date: ____________

🏆 Success Criteria — tick at the END of the lesson:

☐ I can define frequency (Hz) and period (s).

☐ I can use T = 1/f.

☐ I can use f = 1/T and explain why they're inversely related.

Knowledge Organiser: Frequency & Period (L4b)

How to use: Read this before starting. Refer back during independent work. Cover it up for the exit ticket — that tests what you actually remember!

Concept	Details
Frequency (f)	Number of complete waves per second. Hertz (Hz).
Period (T)	Time for one complete wave. Seconds (s).
T = 1/f	Period equals 1 divided by frequency.
f = 1/T	Frequency equals 1 divided by period.
Inverse relationship	High frequency = short period. Low frequency = long period.
Worked example	f = 5 Hz → T = 1 ÷ 5 = 0.2 s.

🧠 Memory Tricks

Frequency = how Fast they come (per second).

"Period" like a class period = a length of time.

Flip it: T and f are always on opposite sides of "1 ÷".

📋 Exam Technique — Every Mark Counts!

1 mark = State / Name / Write the formula.

2 marks = Show the formula + substitute + answer with unit.

3+ marks = Full working + answer + unit. Explain questions need "because".

Golden rule: Write the formula first, every time — even if you get stuck after that, it's still a mark.

Arrival Task – Multiple Choice (circle a letter)

Foundation 🟢

1) What is the highest point of a wave called? A) Trough B) Crest C) Amplitude D) Wavelength

2) What is amplitude? A) How tall the wave is B) How fast it moves C) The colour D) The smell

3) If something happens "frequently", it happens… A) Rarely B) Often C) Never D) Slowly

4) If 5 waves pass a point in 1 second, how many is that per second? A) 1 B) 5 C) 10 D) 0

Middle 🟠

1) Define wavelength. A) Height of the wave B) Distance from one wave to the next C) The wave's speed D) The wave's colour

2) What do you think "frequency" might measure? A) How tall waves are B) How often waves happen each second C) How wide waves are D) The wave's colour

3) If a clock ticks once per second, how many ticks happen in 5 seconds? A) 1 B) 5 C) 10 D) 0.5

4) A "class period" is a length of time. What do you think "period" might mean for a wave? A) The colour of a wave B) The time for one wave to pass C) The height of a wave D) The number of waves

Higher 🔵

1) What is a wavefront? A) A single point on a wave B) A line joining points at the same stage of a wave C) The front of a boat D) The end of a wave

2) An event happens 10 times in 2 seconds. How many times per second? A) 5 B) 10 C) 20 D) 2

3) Event A happens every 0.5 s. Event B happens every 2 s. Which happens more often? A) A B) B C) Same D) Can't tell

4) If frequency tells you how many waves per second, what do you think "period" tells you? A) How many waves in total B) The time for ONE wave C) The colour of the wave D) The height of the wave

Starter: Units Match-Up

Quantity	Unit	Symbol
Frequency
Wavelength
Wave speed
Period

Word bank: Hz (hertz) · m (metre) · m/s · s (second)

We Do Worksheet

Part A: Match Frequency to Period

Use T = 1/f to complete the table.

Frequency (Hz)	Period (s)
2
5
10
4
20

Part B: Reverse It

Use f = 1/T to complete the table.

Period (s)	Frequency (Hz)
0.5
0.1
0.25

Scaffolding Sheet

Frequency & Period

Term	Definition	Unit
Frequency (f)	Waves per second	Hz
Period (T)	Time for 1 wave	s

The Formula

T = 1 ÷ f and f = 1 ÷ T

Write the formula first, then substitute the number you're given, then calculate.

Independent Work – Foundation (Grades U–1)

You've got this! Use your scaffolding sheet. Write the formula first every time. Show your working — even partial working earns marks.

Section A: Multiple Choice

1. Frequency is measured in… [ ] Metres [ ] Hertz [ ] Seconds

2. Period is measured in… [ ] Metres [ ] Hertz [ ] Seconds

3. Frequency means… [ ] Waves per second [ ] Height of a wave [ ] Colour of a wave

4. The formula for period is… [ ] T = 1 ÷ f [ ] T = f ÷ 1 [ ] T = f + 1

Section B: Short Answer

5. State what unit frequency is measured in.

6. State what unit period is measured in.

7. A wave has a frequency of 2 Hz. Use T = 1 ÷ f to calculate the period. Show your working.

Section C: Long Answer (Grade 2 Challenge — scaffolded)

8. (4 marks) Complete the sentences about frequency and period.

Frequency measures how many _________________________ pass a point every _________________________ . [2 marks]

Period measures the _________________________ for _________________________ complete wave to pass. [2 marks]

Section D: Exam-Style

9. (3 marks) A wave has a frequency of 10 Hz. Calculate the period. Show the formula, substitution and answer with unit.

Independent Work – Middle (Grades 1–2)

Push yourself! Show full working for every calculation. Section D is your Grade 3 stretch — give it your best shot.

Section A: Multiple Choice & Recall

1. Which quantity has the unit hertz? [ ] Wavelength [ ] Frequency [ ] Period

2. T = 1/f. If f = 10 Hz, T = … [ ] 10 s [ ] 0.1 s [ ] 100 s

3. Define frequency.

4. Define period.

Section B: Application

5. Complete the table:

Frequency (Hz)	Period (s)
2
5
50
	0.01

6. Explain what it means for two quantities to be "inversely related", using frequency and period as your example. [2 marks]

Section C: Long Answer

7. (4 marks) A student says "frequency and period mean the same thing." Explain why this is wrong. [4 marks]

Section D: Exam-Style (Grade 3 Stretch)

8. (5 marks) A student counts 20 complete waves passing a point in 10 seconds.

(a) Calculate the frequency. [2 marks]

(b) Calculate the period. [3 marks]

Independent Work – Higher (Grades 3–5)

Aim high! Full sentences for explanations. Section D includes Grade 5 challenges — these go beyond the basics. Show the examiner you can reason, not just calculate.

Section A: Recall

1. Define frequency and state its unit. [2 marks]

2. Define period and state its unit. [2 marks]

3. Explain the relationship between period and frequency. [2 marks]

Section B: Application

4. Complete the table and show working:

f (Hz)	T (s)	Working
250
	0.002
50000

5. Two waves have frequencies of 100 Hz and 1000 Hz. Explain, with calculations, which has the shorter period. [3 marks]

Section C: Long Answer

6. (5 marks) Explain why frequency and period are described as "inverses" of each other, and why this relationship always holds true. Use a worked example to support your answer. [5 marks]

Section D: Exam-Style (includes Grade 5 Challenge)

7. (6 marks) A wave source produces 40 complete waves in 8 seconds.

(a) Calculate the frequency. [2 marks]

(b) Calculate the period. [2 marks]

Exit Ticket – Frequency & Period (Foundation U–1)

Name: _________________________ Date: _____________

1) What is frequency the measure of?

2) What unit is frequency measured in?

3) What unit is period measured in?

Exit Ticket – Frequency & Period (Middle 1–2)

1) Define period.

2) f = 4 Hz. Calculate T.

3) T = 0.1 s. Calculate f.

Exit Ticket – Frequency & Period (Higher 3–5)

1) Explain why frequency and period are inverses.

2) T = 0.005 s. Calculate f.

3) Two waves have frequencies of 100 Hz and 1000 Hz. Which has the shorter period, and why?

Frequency & Period

🏆 By the end I will be able to…

🖨️ Pupil Packs

⏱️ 40-Minute Pacing Guide

Arrival Task – Recall from Last Lesson

1. 🟢

2. 🟢

3. 🟢

4. Lead-in 🔢

1. 🟠

2. 🟠

3. 🟠

4. Lead-in 🔢

1. 🔵

2. 🔵

3. 🔵

4. Lead-in 🔢

Starter: Units Match-Up 🔢

📝 Complete the Table

💡 Did You Know?

I Do: Frequency & Period (3.3)

🔄 Frequency, Period & the Link

Frequency vs Period

We Do: Match Frequency to Period 🔢

Independent Work

📝 Your Pack Contains:

🏆 Success Criteria

✅ Tick as you go — Success checklist

Exit Ticket – Check Your Learning

Knowledge Organiser: Frequency & Period (L4b)

🧠 Memory Tricks

📋 Exam Technique — Every Mark Counts!

Arrival Task – Multiple Choice (circle a letter)

Foundation 🟢

Middle 🟠

Higher 🔵

Starter: Units Match-Up

We Do Worksheet

Part A: Match Frequency to Period

Part B: Reverse It

Scaffolding Sheet

Frequency & Period

The Formula

Independent Work – Foundation (Grades U–1)

Section A: Multiple Choice

Section B: Short Answer

Section C: Long Answer (Grade 2 Challenge — scaffolded)

Section D: Exam-Style

Independent Work – Middle (Grades 1–2)

Section A: Multiple Choice & Recall

Section B: Application

Section C: Long Answer

Section D: Exam-Style (Grade 3 Stretch)

Independent Work – Higher (Grades 3–5)

Section A: Recall

Section B: Application

Section C: Long Answer

Section D: Exam-Style (includes Grade 5 Challenge)

Exit Ticket – Frequency & Period (Foundation U–1)

Exit Ticket – Frequency & Period (Middle 1–2)

Exit Ticket – Frequency & Period (Higher 3–5)

We Do – Class Evidence

🎓 TA Focus

🎯 Cold Call

📺 Waves in a Ripple Tank

🏆 Class Progress Board

🎉 Lesson Complete!