Mirrors
Comprehensive notes, formulas, and practice questions for Mirrors.
Mirrors
Mirrors & Reflection
What you'll learn
- How a plane mirror forms an image by reflection of light.
- Characteristics of mirror images: same size, laterally inverted, virtual.
- Uses of mirrors in daily life — dressing, rear-view, dentist's mirror, periscope idea.
- Safe handling of mirrors and difference between reflection and shadow formation.
Key concepts
Level 1 — Reflection basics
Verbal: When light hits a shiny surface, it bounces back — this is reflection. A smooth surface like a plane mirror reflects clearly.
Visual (text diagram): Incident ray from object hits mirror at angle → reflected ray travels to eye → image appears behind mirror.
Image properties (plane mirror):
| Property | Object | Image in plane mirror |
|---|---|---|
| Size | Actual height | Same height |
| Distance | 2 m in front | Appears 2 m behind mirror |
| Orientation | Right hand | Looks like left hand (lateral inversion) |
Level 2 — Applications and periscope
Virtual image: Cannot be caught on screen — appears behind mirror; rays appear to come from there.
Uses: Comb mirror (personal grooming), car rear-view (see traffic behind), side mirrors on buses.
Periscope (concept): Two plane mirrors at 45° let you see over walls — submarines and parade viewing (NCERT extension).
Safety: Never reflect sunlight into eyes — concentrated reflected light can harm vision.
Worked example
You stand 1.5 m in front of a bathroom mirror. Where does your image appear?
Step 1 — Plane mirror: image distance behind mirror = object distance in front
Step 2 — You are 1.5 m in front → image appears 1.5 m behind mirror
Step 3 — Total separation between you and your image = 1.5 + 1.5 = 3 m
Step 4 — Image is upright, same size, laterally inverted (parting on wrong side)
Common mistakes
| Mistake | Why it happens | Fix |
|---|---|---|
| Image is inside the mirror glass | Looks embedded | Image is virtual — appears behind surface |
| Mirror shrinks distant objects | Confusing with curved mirrors | Plane mirror: same size |
| Reflection = shadow | Both involve light blocking/bouncing | Reflection = bounce; shadow = block |
| Any shiny thing is a mirror | Foil crinkles scatter light | Plane mirror needs smooth flat surface |
Quick check
- List two properties of an image formed by a plane mirror.
- What is lateral inversion? Give an example with letters (e.g. AMBULANCE).
- Name two everyday uses of plane mirrors.
- Can you obtain a mirror image on a white screen? Why or why not?
Open the Practice tab for graded questions on Mirrors & Reflection.
Key Takeaways (TL;DR)
- What you'll learn
- Key concepts
- Worked example
- Common mistakes
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