Have you ever watched a shadow play? In Karnataka, Togalu Gombeyaata is a famous puppet shadow theatre. When light shines behind a puppet, we see its shadow on a screen. The shadow shows the shape of the puppet! This chapter uses the idea of shadows to help us understand the shapes of solids (3-D objects).
What will we learn?
We will identify common 3-D (solid) shapes — cube, cuboid, cylinder, cone, and sphere — and understand what flat (2-D) shadow shapes they make.
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Key Concepts
3-D shapes (solids): Objects that have length, width, and height.
Cube: Has 6 equal square faces. Example: a dice.
Cuboid: Has 6 rectangular faces. Example: a brick, a matchbox.
Cylinder: Has 2 circular flat faces and 1 curved face. Example: a tin can, a drum.
Cone: Has 1 circular flat face and 1 curved surface coming to a point. Example: an ice cream cone.
Sphere: Completely round, no flat face. Example: a ball.
- Shadow = flat shape: When light falls on a 3-D object, the shadow looks like a 2-D shape.
- Cube / Cuboid shadow: square or rectangle
- Cylinder shadow: rectangle or circle (depending on direction)
- Cone shadow: triangle or circle (depending on direction)
- Sphere shadow: always a circle
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Worked Examples
A dice is rolled onto a table and light shines from the side. What shape is its shadow?
A dice is a cube; its side shadow is a square.
A tin can (cylinder) is placed upright. Light shines from the side. What shadow does it make?
The shadow of an upright cylinder from the side is a rectangle.
What shadow does a ball (sphere) make in any direction?
A sphere always makes a circular shadow.
An ice cream cone is placed with its point up. Light shines from the side. What shadow appears?
The shadow of a cone from the side is a triangle.
Name a 3-D object that has no flat face at all.
A sphere (ball) has no flat face — it is completely curved.
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Common mistakes
- A cylinder is NOT a circle; it is a solid 3-D shape. Its flat face is a circle.
- Students confuse cubes and cuboids. Both have 6 faces, but a cube has ALL faces equal (square), while a cuboid has rectangular faces.
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Summary
Solid shapes around us are 3-D. They can be cubes, cuboids, cylinders, cones, or spheres. When light falls on them, we see flat 2-D shadows — squares, rectangles, triangles, or circles. Shadow plays help us understand shapes in a fun way!