Concave and Convex Mirrors

Introduction:

In this experiment we examine the images formed by convex and concave mirrors.  By way of direct observation and sample calculations, we will find the general behavior of such images formed.

Steps:

Convex Mirrors

In our physical observation of convex mirrors we found that objects placed at further distances would appear smaller than they really were.  This effect became less exaggerated as you come closer to the mirror (it seems to be more like the appropriate size).

When looking at the convex mirror at a distance, we note that the image looks further away than the object actually is.  I am holding up the camera phone (black sweater). Clearly, the cameras distance, relative to the mirror, is closer than imaged.

Calculations involving magnifications with a convex mirror:

Sample calculations for a convex mirror with actual measurements on the figure shown.

Concave Mirrors

Concave mirrors offered a much different perspective once viewed at distances greater than the focal length. Images were inverted and smaller than the objects really were.  Although the image was inverted, we still observed the same closer-to-the-real-size effect as we did with convex mirrors.  As we neared the concave mirror, though, there was a point where no clear image could be seen.  We note this to be the focal point.   The diagrams at the conclusion of this experiment will illustrate this phenomenon.

The inversion effect is clear in this photo of a concave mirror.  I (black sweater) observe the actual relative distance to be  closer than was imaged in the mirror.

Calculations involving magnifications with a concave mirror:

Sample calculations for a concavemirror with actual measurements on the figure shown.

Questions/Conclusions:

 The image descriptions can be summarized with ray diagrams of convex and concave mirrors shown below.

Convex mirror:

Sample ray diagram for convex mirrors.

Concave mirror:

Sample ray diagram for concave mirrors.

The inversion effect is clearly seen by they sketch above, but the diagrams below illustrate exactly when a right side up image may be observed.  It is clear an object at a focal point cannot focus for a concave mirror as the rays reflected come back parallel.

General behavior of a concave mirror found using 3 ray diagrams.