You will learn
- Describe images in a plane mirror.
- Explain left-right reversal.
- Use two mirrors to change a light path.
- Explain a periscope.
Version 0.2 · expanded edition · built from cited public sources Content is based on the official frameworks and sources listed under Sources and standards. No official endorsement is claimed. Written in the style of common primary school assessments. No exam result is promised.
Student lesson
- A plane mirror makes an image the same size.
- The image is reversed left to right.
- Mirrors change the direction of light.
- Periscopes use two mirrors.
Words to know
a flat mirror
the picture we see in a mirror
turned left to right
a tube with mirrors for seeing over obstacles
1. Discover: The mirror writing
Dziedzi holds her name up to the mirror and the letters flip. “They are backwards!” she laughs. Her teacher says, “The image is reversed left to right.” Then they build a cardboard periscope with two mirrors so she can see over a wall. “Light takes a zigzag path,” Dziedzi realises.
Think: How many mirrors does a periscope need?
2. Understand: Mirrors
Idea 1: Images in a mirror
A plane mirror shows an image the same size as the object and the same distance behind the mirror. Left and right appear reversed.
Idea 2: Changing direction
Mirrors turn light rays. Placing a mirror at 45 degrees turns a beam through 90 degrees. Two mirrors can send light around an obstacle.
Idea 3: Periscopes
A periscope uses two parallel mirrors at 45 degrees. It lets submarine crews and people at crowds see over obstacles.
3. Worked examples
Example 1 (I show you): Predict
Write a letter R in a mirror.
- Reversed.
- Flipped.
- Backwards R.
Answer: It appears reversed.
Example 2 (We do it together): Distance
Object 20 cm from mirror.
- Image behind.
- Same distance.
- 20 cm.
Answer: The image is 20 cm behind the mirror.
Example 3 (You try): Device
Periscope.
Show the steps and answer
- Two mirrors.
- Angled 45.
- See over wall.
Answer: It needs two mirrors.
Did you know?
Ambulances have mirror writing on the front so that drivers see the word AMBULANCE the right way round in their rear-view mirrors.
Why this matters
Mirrors help us see around corners, check traffic and study tiny details.
4. Explore: Build a periscope
Build a cardboard periscope using two plastic mirrors.
- Cut two windows in a carton (adult help).
- Fix mirrors at 45 degrees.
- Look through the lower window.
- See over an object.
Think about it: what did you notice?
What did you notice? The image was upright but reversed left-right.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- A ___ mirror is flat.
- An ___ is the picture we see.
- A ___ lets us see over obstacles.
- Letters appear ___.
Guided practice
Question 1. What is a plane mirror?
Flat mirror.
Question 2. What is an image?
Picture in mirror.
Question 3. What is a periscope?
Mirror tube.
Independent practice
Level 1: Start
- What is a plane mirror?
- What is an image?
- What is a periscope?
- How many mirrors?
- What is reversed?
Level 2: Grow
- Why 45 degrees?
- Why use two mirrors?
- Why mirror writing?
Level 3: Stretch
- Draw a periscope.
- Write a name in a mirror.
- Measure image distance.
Answers are in the answer key below. Try first, then check.
6. Apply: Science in everyday life
Explain how a periscope works.
Show a sample answer
Use rays.
Another one. Tell a family member one thing from this lesson. Use the words you learned.
Show a sample answer
A clear sentence that uses at least one word from Words to know.
7. Common mistakes
Fix: Left-right.
Fix: Two.
8. Lesson summary and revision card
- I can describe images in a plane mirror.
- I can explain left-right reversal.
- I can use two mirrors to change a light path.
- I can explain a periscope.
9. Check and master
Answer all 14 questions. You will see feedback after each one.
Your result appears here after you answer every question.
10. Key takeaways
- A plane mirror makes an image the same size.
- The image is reversed left to right.
- Mirrors change the direction of light.
- Periscopes use two mirrors.
11. Next lesson
Next lesson: Transparent materials. Keep going with the next idea in this course.
Exam practice
These questions are written in the style of common school and international primary assessments. Try them on your own, without looking back. Then check your answers in the marking guide. The marks are shown in brackets.
- Describe a plane mirror image. [3 marks]
- Explain mirror writing. [2 marks]
- How does a periscope work? [3 marks]
- Safety rule? [2 marks]
Total: 10 marks.
Marking guide and model answers
- Same size [1]; same distance [1]; reversed [1]
- Reversed [1]; reads right in a mirror [1]
- Two mirrors [1]; 45 degrees [1]; light redirected [1]
- Plastic mirrors [1]; reason [1]
Score guide: 9 to 10 = secure. 6 to 8 = nearly there, revise the parts you missed. Under 6 = work through the lesson again with a grown-up.
Printable worksheet
- What is a plane mirror?
- What is an image?
- What is a periscope?
- How many mirrors?
- What is reversed?
- Why 45 degrees?
- Why use two mirrors?
- Why mirror writing?
- Draw a periscope.
- Write a name in a mirror.
Homework
Write your name in mirror writing and check it with a mirror.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 1. What is a plane mirror? | Flat mirror. | 1 |
| 2. What is an image? | Picture in mirror. | 1 |
| 3. What is a periscope? | Mirror tube. | 1 |
| 4. How many mirrors? | Two. | 1 |
| 5. What is reversed? | Left-right. | 1 |
| 6. Why 45 degrees? | Turns light 90. | 1 |
| 7. Why use two mirrors? | Move light twice. | 1 |
| 8. Why mirror writing? | Reads right in mirrors. | 1 |
| 9. Draw a periscope. | Diagram. | 1 |
| 10. Write a name in a mirror. | Drawing. | 1 |
| Total | 10 |
Independent practice answers. Level 1: 1 Flat mirror.; 2 Picture in mirror.; 3 Mirror tube.; 4 Two.; 5 Left-right.. Level 2: 1 Turns light 90.; 2 Move light twice.; 3 Reads right in mirrors.. Level 3: 1 Diagram.; 2 Drawing.; 3 Table..
Quiz answers: 1 B, 2 C, 3 A, 4 B, 5 C, 6 A, 7 B, 8 C, 9 A, 10 B, 11 C, 12 A, Challenge 1 B, Challenge 2 C.
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Describe images in a plane mirror | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Explain left-right reversal | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Use two mirrors to change a light path | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Explain a periscope | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Courseversity badge thresholds (overall quiz score): Gold = 90–100%; Silver = 80–89.9%; Bronze = 70–79.9%. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: “A mirror image is flipped upside down.” Left-right.
- Explain another way: use real objects, pictures or actions first, then words.
- Show a simpler example: Explain mirror images and periscopes.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
For parents and guardians
In this lesson your child studies mirrors and periscopes. You do not need to be an expert to help.
- Play mirror-writing games.
- Ask “Why is it backwards?”
- Use safe mirrors.
- Ask “how do you know?” after each answer, and listen.
- Praise effort, not only right answers. Mistakes are how we learn.
- Ten to fifteen minutes a day is better than one long session.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: describe images in a plane mirror; explain left-right reversal; use two mirrors to change a light path; explain a periscope.
Prerequisite knowledge. Grade 3 physical ideas: forces, materials, and how to measure and record in fair tests.
Materials. Plastic mirrors, cardboard, tape. Low-resource options: use chalk or charcoal on a board or wall, drawings in the sand, and objects from the classroom instead of printed materials.
Preparation. Cut cartons.
Suggested duration. 45–60 minutes. It can be split into two shorter sessions.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Show writing in a mirror and ask, “What is odd?”
Explanation (10 min). Teach mirrors.
Guided activity (10 min). Learners build.
Independent activity (10 min). Learners test.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Key questions. Reversed? Upright? How many mirrors?
Teacher explanation notes. Start with real objects and safe, hands-on observation. Then talk about what was seen, then draw and write. Always say “how do you know?”. Keep to the safety notes, and use local, safe materials.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and pictures, short sentences and a partner. Let learners point, show or draw instead of writing. Extension. Ask learners to find a new example at home and explain how they know.
Formative assessment. Listen to learners read and explain, ask “how do you know?”, and check the independent work.
Misconceptions. “A mirror image is flipped upside down.” Left-right.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz, the 10-mark exam practice and the worksheet on this page. All answers and marking guides are in the answer sections above. Re-check every answer before use.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Explain mirror images and periscopes. Enrichment. Look for one new example near your home or school, draw it and explain it to someone. Homework. See above.
Teacher reflection. After teaching, record: which ideas learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
This lesson is based on the sources below, and no official endorsement is claimed. Reference starting points: Next Generation Science Standards, Cambridge Primary Science and the IB Primary Years Programme. Where a standard code is named, it points to the official framework.
Research used to shape this lesson. Courseversity Science curriculum, Grade 4 Unit 4, topic 4; Next Generation Science Standards, waves and their applications (light); Cambridge Primary Science Stage 4, physics: light and dark; IB Primary Years Programme, how the world works. These sources informed the lesson.