Answers to all "Let Us Enhance Our Learning" questions of Chapter 11, Light: Shadows and Reflections (NCERT Class 7 Science, Curiosity, 2026-27): luminous objects, transparent, translucent and opaque materials, shadows, the pinhole camera, reflection, plane mirrors, lateral inversion and the periscope. All 12 questions are answered, with the key answer highlighted.
Light travels in a straight line. An opaque object blocks light and forms a shadow on the side away from the light. A pinhole camera forms an inverted image. A plane mirror forms an image that is erect, of the same size, as far behind the mirror as the object is in front, and laterally inverted (left and right interchanged).
Pole Star and Sun (both are stars, which give out their own light). Mars and Venus (planets), the Moon and a mirror only reflect light.
Pole Star and Sun
| Column A | Column B |
|---|---|
| Pinhole camera | Forms an inverted image |
| Opaque object | Blocks light completely |
| Transparent object | Light passes almost completely through it |
| Shadow | The dark region formed behind the object |
Pinhole camera – inverted image; opaque object – blocks light; transparent object – lets light pass; shadow – dark region behind the object.
Only Rekha. Light travels in a straight line, and only Rekha's pipe runs straight to the candle. The pipes of Sahil, Patrick and Qasima are bent (they branch off at an angle), so light from the flame cannot reach their eyes.
Rekha, because only her pipe is straight and light travels in straight lines.
(d). The shadow is always formed on the side opposite to the light source. In (d) the Sun is at the top right and the shadow falls towards the bottom left, away from the Sun. (In (a) and (c) the shadow is on the same side as the Sun, which is impossible, and in (b) the shadow is a round patch under the boy, which would happen only when the Sun is directly overhead, but here the Sun is low and to one side.)
(d): the shadow falls on the side opposite to the Sun.
(i) → (b), larger shadow; (ii) → (a), smaller shadow.
| Column A | Column B |
|---|---|
| If the torch is close to the ball | The shadow would be larger |
| If the torch is far away | The shadow would be smaller |
| If the ball is removed from the set-up | A bright spot would appear on the screen |
| If two torches are present on the left side of the ball | Two shadows would appear on the screen |
Torch close – larger shadow; torch far – smaller shadow; ball removed – bright spot; two torches – two shadows.
The image is inverted (upside down): draw the tree with its trunk at the top and its leafy crown at the bottom. (It is also usually smaller than the tree, and left and right are interchanged.) This happens because light from the top of the tree passes in a straight line through the pinhole and reaches the bottom of the screen, and light from the bottom reaches the top.
Draw the tree upside down (trunk at the top, crown at the bottom), because rays crossing at the pinhole form an inverted image.
The name in the mirror appears reversed from left to right: the letters are written backwards and the first letter appears at the right end. For example, in "RAVI" the letters appear in the order I, V, A, R from left to right, and the R appears flipped. This is called lateral inversion: a plane mirror interchanges the left and right sides of an object (the top and bottom are not interchanged).
The writing appears reversed from left to right (mirror writing) because a plane mirror causes lateral inversion.
Sample observations: 9 AM – about 2.5 m (long, towards the west); 12 PM – about 0.5 m (shortest); 4 PM – about 2 m (long, towards the east).
(i) The shadow is shortest at 12 PM (noon).
(ii) At noon the Sun is highest in the sky, almost overhead, so its light falls nearly straight down and the shadow is short. In the morning and late afternoon the Sun is low, so its rays fall slantingly and the shadows are long.
Shortest at noon, because the Sun is highest in the sky then; it is low in the morning and afternoon, making shadows long.
(i) Both statements are true. A plane mirror laterally inverts images, but T and O are symmetrical about a vertical line, so when their left and right sides are interchanged they look the same.
(i) Both are true.
Yes. Fix one plane mirror at each bend, at an angle of 45° to the tube, with the two mirrors parallel to each other and facing each other. Light entering the top opening falls on the upper mirror, is reflected straight down the tube to the lower mirror, and is reflected again into the eye at the bottom opening. Then you can see objects above a wall or over an obstacle.
Yes: fix the two mirrors at the two bends, each at 45° to the tube and parallel to each other.
The Sun is a large source of light, not a point. When the bird is high up, light from different parts of the Sun reaches the ground around the bird's small body, so the shadow is spread out and fills in with light; it becomes too faint and blurred to see. When the bird comes close to the ground, its body blocks the light more completely over a small area, and a clear, dark shadow is formed (just like a ball near the wall gives a sharp shadow).
High up, light from all parts of the large Sun spreads around the small bird, so its shadow is too faint to see; close to the ground, the bird blocks the light sharply and a clear shadow forms.
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