The big picture
Switch the torch off, and the shadow disappears. Ten ideas, all from one habit.
| Idea | Remember | Example |
|---|---|---|
| Straight lines | In air, light goes straight. A wall stops it. | three punched cards, lined up |
| Shadows | A dark shadow needs light, an opaque object, a surface. | the neem tree at noon |
| Size and shape | Nearer the lamp, bigger. Turn it, the outline changes. | a puppet on a cloth |
| Pinhole | Top lands low, bottom lands high. | a shoebox camera |
| Bouncing | Same slant out as in. | a tilted steel plate |
| Mirror image | Same size, upright mirror: same way up. Left-right swapped. | AMBULANCE, painted backwards |
| Rough surfaces | Every patch faces its own way. No picture. | a wall, a rippled pond |
| Own light | A luminous object makes its own light. A non-luminous object does not. We see it when light from another source bounces off it. | a candle flame, the Moon |
| Through materials | An opaque material blocks all the light. A transparent material lets nearly all of it pass. A translucent material lets part of it pass. | plastic bag, cotton sheet, tile |
| Periscope | A simple periscope has two plane mirrors. They are parallel, each tilted at 45°. Light turns twice and reaches your eye. | a tube for seeing over a wall |
Open Chapter 11, Light: Shadows and Reflections, in your NCERT book. Ask of each question: which habit of light is this?