Here, we’ll show you how to draw a ray diagram for a concave mirror when the object is between the focal point and the mirror.

Here is a diagram of a concave mirror showing the principal axis The Principal Axis

Here is the focal point, F x F The Focal Point

And here’s the center of curvature, C. It is twice the distance from the mirror as the focal point, F xx CF The Center of Curvature

In this example, the object is between the focal point and the mirror. xx CF The Object

We’ll start by drawing a horizontal line from the top of the object, to the surface of the mirror (click). Remember, it must be parallel to the principal axis xx CF

This ray is reflected back from the mirror (click) and goes through the focal point like this xx CF

The next thing we do is draw a straight line through the center of curvature, C and the top of the object (click) We extend it to the surface of the mirror xx CF

A ray from the top of the object will travel along this line and strike the mirror (click). Because this goes through the center of curvature, it will be reflected back along the very same path, xx CF

Like this xx CF

Notice that the purple and green rays are diverging rays. They are moving apart from each other so they will not cross in front of the mirror to form a real image. xx CF Diverging rays

Even though these rays do not actually go though the mirror, we’ll extend the purple ray back, behind the mirror (click) like this xx CF

And the green ray back behind the mirror, like this. xx CF

When we see rays coming toward us, our brain assumes they are travelling in a straight line from their source. xx CF

So looking from the front of the mirror, these rays seem to be coming from the point where these dotted lines intersect behind the mirror xx CF Point of Intersection

So this is where the top of the object will be in the image. xx CF Top of the Object in the Image

The bottom of the object is sitting on the principal axis xx CF Top of the Object in the Image Bottom of the Object

So the bottom of the object in the image will appear on the principal axis, directly underneath the top xx CF Top of the Object in the Image Bottom of the Object Bottom of the Object in the Image

Now that we know where the bottom and the top of our image is, we can draw it in (click). xx CF Top of the Object in the Image Bottom of the Object Bottom of the Object in the Image

We can use this ray diagram to describe the image formed when the object is between the focal point and the surface of a concave mirror. When the object is between the focal point and a concave mirror: 1.The image is larger than the object 2.The image is behind the mirror 3.The image is right side up, not inverted 4.The image is a virtual image

Firstly, we see that the image is larger than the object. A concave mirror used this way acts as a magnifier. When the object is between the focal point and a concave mirror: 1.The image is larger than the object 2.The image is behind the mirror 3.The image is right side up, not inverted 4.The image is a virtual image

Secondly, the image appears to be behind the mirror. But remember, no rays actually go through the mirror When the object is between the focal point and a concave mirror: 1.The image is larger than the object 2.The image is behind the mirror 3.The image is right side up, not inverted 4.The image is a virtual image

We can see that the image in this case is right side up, rather than inverted. This is always true when the object is between the focal point and the surface of this type of mirror When the object is between the focal point and a concave mirror: 1.The image is larger than the object 2.The image is behind the mirror 3.The image is right side up, not inverted 4.The image is a virtual image

And because the image is formed from rays that seem to be coming from behind the mirror, shown as dotted lines rather than actual solid rays, this is a virtual image, not a real image. When the object is between the focal point and a concave mirror: 1.The image is larger than the object 2.The image is behind the mirror 3.The image is right side up, not inverted 4.The image is a virtual image