Light Shadows and Reflections — Question 10
Back to all questionsIn scenario (i), the ball is closer to the torch and away from the wall, so the shadow would be large and blurry on the wall. So the correct representation of scenario (i) will be (b). In scenario (ii), the ball is closer to the wall and away from the torch, so the shadow would be sharp and small. So the correct representation of scenario (ii) will be (a).
Chapter 11: Light
Reflection follows two laws: angle of incidence equals angle of reflection, and all rays are in the same plane. Plane mirror images are virtual, erect, same size, and laterally inverted. Concave mirrors converge light (used in torches, dentist mirrors). Convex mirrors diverge light (used in rear-view mirrors). Dispersion splits white light into VIBGYOR through a prism. Rainbows are natural dispersion by water droplets.
Theme: Physics | Difficulty: Age-appropriate for Class VII
Key Formulas & Equations
| Formula / Equation | When to Use |
|---|---|
| Law 1: Angle of incidence = Angle of reflection (∠i = ∠r) | First law of reflection |
| VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red | Spectrum colours in order |
Must-Know Concepts
- Two laws of reflection: ∠i = ∠r; same plane
- Plane mirror: virtual, erect, same size, laterally inverted, equal distance behind
- Lateral inversion: left-right swap (AMBULANCE written in reverse)
- Concave mirror: converges light, uses = torch, headlight, dentist, solar cooker
- Convex mirror: diverges light, wider view, uses = rear-view mirror
- Real image: on screen; Virtual image: cannot be on screen
- Dispersion: white light through prism gives VIBGYOR spectrum
Common Mistakes to Avoid
- Thinking plane mirror image is real — it is virtual
- Confusing lateral inversion with upside-down
- Thinking white light is pure — it is a mixture of 7 colours
Scoring Tips
- Draw ray diagrams with incident ray, normal, reflected ray, and angles
- List 5 properties of plane mirror image
- Compare concave and convex mirrors with uses