Ray - Definition with Examples

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What is a ray? 
In geometry, a ray can be defined as a part of a line that has a fixed starting point but no end point. It can extend infinitely in one direction. 

ray in geometry

On its way to infinity, a ray may pass through more than one point. 
When naming a ray, it is denoted by drawing a small ray on top of the name of the ray.
 

Here, the starting point of ray PQ is P and on its way to infinity, it passes through point Q. 

Representing a ray in geometry

We use rays while drawing angles
 

Here, each of these angles is made up of two rays. The vertex of the angles is the starting point of the rays.

Using ray in geometry to draw angles

  Fun Facts

  • The sun rays are an example of a ray. The sun is the starting point or the point of origin and its rays of light extend indefinitely in our solar system. 
 

let's sing Let's sing!

A ray is a part of a line.
You see it in rays of the sun that shine,
Or in the arms  angle to align!
 

let's do it Let's do it!

Instead of handing out math worksheets on lines, line segments and rays, show your children how the sun rays are an example of geometric rays, where in the sun is the starting point and how its rays reach the Earth. 
You can further use a torch to explain rays.
 

related math vocabulary Related math vocabulary

 
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