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LAUNCH · Science · Week 3

Use: Calculating Magnification

Aut1·W3 (Use) — Calculate magnification (links Maths; record in spreadsheet).

Edexcel GCSE Biology 1BI0 Foundation · Paper 1 · Topic 1Pearson Edexcel GCSE (9–1) Biology 1BI0 (Foundation, grades 1–5); GCSE Combined Science 1SC0 F where appropriate; AQA UAS science units
🎯 Learning Objective: I can calculate magnification, image size and actual size, and convert between mm and µm.

✅ Success Criteria

  • I can state the magnification equation and rearrange it.
  • I can convert between millimetres and micrometres correctly.
  • I can calculate total magnification from the two lenses.
🔗 Assessment link: AQA UAS: 'Using a microscope'; 'Scientific calculations'.

LAUNCH · one 40-minute session. Title orientation is untimed; keep the full 15-minute independent task.

Teacher timing and core practice

40-minute session: Arrival 3; overview 1; I Do 1 4; We Do 1 4; I Do 2 3; We Do 2 4; independent work 15; feedback and next step 3; exit 3. Title orientation is untimed. The optional two-minute evidence check sits inside independent time. Keep extra practice available; use the core question, a contrasting example and a recheck before extending.

🖨 Teacher print tools

Resources · shared task, PDFs and video
🚪 Arrival · start this as you come in

Arrival task — pick your tier

◆ Supported

Write the magnification equation from the word bank.

🗺️ Today at a Glance

Three things we do today

1.

Equation and rearrangement

2.

Unit conversion

3.

Total magnification

👩‍🏫 I Do · watch me think

Watch me work through one

🧠 Watch me think: Image is 40 mm across. Actual cell is 0.1 mm. First question I always ask: are the units the same? Yes, both millimetres, so I can divide. 40 ÷ 0.1 = 400. Magnification ×400. No units on the answer. If they had NOT matched, converting would have been step one, before anything else.

📖 Key definitions

  • magnification — How many times bigger the image is than the real object.
  • image size — The size of the object as it appears (measured on the picture).
  • actual size — The real size of the object.
  • micrometre (µm) — One thousandth of a millimetre. 1 mm = 1000 µm.
❌ Common mistake: Magnification has units.
✅ Actually: It is a ratio of two lengths, so the units cancel. ×400, never 400 mm.
🤝 We Do · together

Work it out before you tap

Pen down, answer in your head, then check.Found 0/5
Image 30 mm, actual 0.15 mm. Magnification?
Magnification ×500, image 25 mm. Actual size?
Eyepiece ×10, objective ×40. Total?
Convert 0.02 mm to µm
Convert 750 µm to mm

👩‍🏫 I Do 2 · the evidence loop

Evidence loop

🧠 Watch me think: Set every calculation out the same way, because the method carries marks even when the answer slips: equation, then units check, then substitution, then answer with the multiplication sign. Four lines, every time. You write them, not me.

Assessor witness · what the adult is watching for

  • Stated and rearranged the magnification equation.
  • Converted correctly between mm and µm.
  • Calculated total magnification from two lenses.

📸 Capture: Photograph the pupil's four-line working for one calculation — the layout is the evidence, not just the answer.

🤝 We Do 2 · sort, then write

Spot the error

Sort, don’t guess. Put each card in the right bin.Sorted 0/6
Magnification = ×400
Magnification = 400 mm
40 mm ÷ 100 µm = 0.4
Actual = image ÷ magnification
Actual = image × magnification
Total mag = eyepiece × objective
● CORRECT
■ ERROR

✏️ Independent Work

Your turn — pick your tier

15 minutes. Choose the tier your adult rings for you.

Use the task time to work, check and improve: reserve up to two of these 15 minutes for an evidence check with your adult or a partner, then act on one useful point. Point, say, sign, demonstrate, write or use an agreed scribe. Manual pause stays available.

15:00

◆ Supported

Six calculations with the equation and a worked example printed on the sheet. Units already matched.

▲ Standard

Eight calculations including two that need unit conversion first, plus one rearrangement.

★ Stretch

Eight calculations including conversions and rearrangements, then record your results in the spreadsheet and add a column showing total magnification for each lens pair.

🔁 Lundy Loop

Where what you say changes something

This is where your voice changes what happens next.

🛡 Space

Calculation under pressure is its own barrier. The equation stays on the board all lesson — you are not being tested on remembering it today.

🗣 Voice

If you think my worked example is wrong, stop me. Twice a year somebody is right.

👂 Audience

Your spreadsheet goes into your Topic 1 folder and is revisited at W7.

⚙ Influence

The class decides which calculation type gets extra practice before the assessment.

🎫 Exit Ticket

Before you go

◆ Supported

Write the magnification equation.

magnification = image size ÷ actual size

Slide 1/10
🏅📸✍️

Use: Calculating Magnification — banked!

LAUNCH Science · Week 3 ✅

I can state the magnification equation and rearrange it. I can convert between millimetres and micrometres correctly. I can calculate total magnification from the two lenses.
⏸ MID-POINT PEER CHECK

Pens down — quick partner check!

📣 Show your partner where you’re up to. Check together against today’s success: I can state the magnification equation and rearrange it. and I can convert between millimetres and micrometres correctly.. If something’s missing, help them add it — kindly.

Optional check: use up to two minutes of the independent-work allocation. Manual pause is available if you need more time.

Lesson resources · W3L2

LAUNCH Science · W3L2 · lesson resources

Choose the relationship

Choose one shared task or resource within the current lesson stage. Keep the lesson’s 40-minute timetable and 15-minute independent work.

We Do · Choose the relationship

Work in pairs: one chooses the formula; one checks the units. Swap.

  1. A Image 20 mm; actual 0.1 mm. Find M.
  2. B Image 50 mm; actual 0.5 mm. Find M.
  3. C M = ×400; actual 0.05 mm. Find image size.

Discuss, point, write or dictate your first reason. Use one example first; extend only if there is time.

Reveal shared reasoning after an attempt

A: 20 ÷ 0.1 = ×200.
B: 50 ÷ 0.5 = ×100.
C: 400 × 0.05 = 20 mm.
Keep units for lengths; magnification is a ratio.

This page keeps your writing while it stays open. It does not save or send it.

Model explanation and diagram
Scientific visual for this lesson A local vector model used to support observation and reasoning. Labels and explanations are supplied in the lesson. 1 mm 1000 µm match units → divide image by actual → check scale
A model illustration. Use the stated measurements for calculations.

Name the unknown, match the units, select the relationship, substitute, then check. Magnification is a ratio: write ×200, not 200 mm.

Watch for: 50 µm is 0.05 mm, not 50 mm. A correct final value is not evidence that the unit route was understood.

Give a smaller support cue

1. Name the missing value. 2. Match the units. 3. Choose M = I ÷ A, I = M × A or A = I ÷ M. 4. Show each line of working.

Optional video · Microscopy

Watch for: What is the difference between making an image bigger and resolving more detail?

Use a short relevant extract within I Do, then pause for an explanation. The clip replaces part of the modelling time.

Open the freesciencelessons video in a new tab

No-video version · use the same question
Scientific visual for this lesson A local vector model used to support observation and reasoning. Labels and explanations are supplied in the lesson. apparent size separate detail not the same property

Magnification compares image size with actual size. Resolution is the ability to distinguish two close points as separate. Increasing size alone does not reveal more detail.

Internet is needed for the optional clip. It is concept teaching; viewing it is not completion of a practical.