Sections Of Solids: Slicing And Shadows

We come across a number of objects of different shapes and sizes in our day to day life. There are golf balls, door mats, ice-cream cones, coke cans and so on. These objects have different characteristic properties such as length, breadth, diameter, etc., which set them apart from one another. But no matter how different their dimensions are, all of them occupy space and have three dimensions. So they are referred to as three-dimensional or solid shapes. In this article, we will discuss views of different sections of solids.

Viewing Different Sections of Solids

A 3D object can be viewed in different ways. Two of them are:

  • Cutting or Slicing
  • Shadow Play

Cutting or Slicing

Before we go ahead with slicing a 3D object for viewing different sections of solids, let us know about the term ‘cross-section’.  A cross-section is the exposed surface of a solid that you get when you make a cut through it. Thus, it does not contain any piece of the original face. It all comes from “inside” the object.

One way to view a 3D object is by cutting or slicing it so as to obtain its cross-section. So let us say, you take a cheese block. The cheese block is like a cuboid with a square face. Now if you slice or cut it with a knife vertically, a square cross-section is obtained. And when you slice it horizontally, a rectangular cross-section is obtained. Similarly, you can slice along different axes to get different cross sections of solids.


Shadow Play

Shadows are another way to view sections of solids in two dimensions. Let us demonstrate it through an activity. You will require a source of light (e.g., a torch), a few solids (cuboid, cone, sphere, etc.) and a screen for the activity. The steps are:

  • Place a solid in front of the screen.
  • Bring the torch in front of the solid from the side opposite to the screen.
  • View the shadow of the solid on the screen.

Shadow Play
You will note that the shadow is triangular for a cone, square or rectangular for a cuboid, square for a cube and a circle for a sphere. These are the 2D views of the 3D shapes.

Practise This Question

We get a cylinder when we rotate a rectangle about its side