The problem with showing just a single ray entering the eye is that it gives no information as to where the light originates from (ie the position of the object).

 

 

 

The object could be close to the eye, like this:

 

 

 

or the object could be far from the eye, like this:

 

 

 

 

 

To solve this we will frequently draw two rays from the object leading to the eye. We call this a light cone.

 

 

 

 

 

 

Caution
The eye symbol is taken to be an indication as to the position of an observer. Thus we do not need to actually show the rays actually going into the eye. As above, it is preferable to draw the cone wider than the eye so that the cone shape is very apparent.

 

Example: Drawing a Light Cone for an Image in a Mirror
Draw a light cone to show how the observer sees an image of the object.   As for any reflection problem, locating the image is usually the first thing to do: Then draw a single ray passing into the top of the eye: Then draw a ray passing into the bottom of the eye: You can see the light cone of two rays starting from the point object and diverging as it moves towards the eye.

 

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