Will the size of the field of view vary depending on whether a convex or concave mirror is used?

Delanie Wheeler
Science Fair
10/24/13

Table of Contents

Title Page………………..1
Table of Contents……2
Abstract………………….3
Procedure……………….4
Results……………………5
Work Cited……………..6

Abstract

Will the size of the field of view vary depending on whether or not a convex or a concave mirror is used? If an object is viewed through a concave mirror instead of a convex mirror, then the field of view will increase. Convex mirrors will show a larger field of view. The procedure followed was to use two concave and convex mirrors that were the same size and to take a picture of the field of view that they both showed. Then, after the pictures were printed, use them to measure the area of the two fields of view. This was repeated five times and an average was obtained. The results were that the convex mirror’s field of view was larger than the concave mirror’s field of view. The convex mirror’s average field of view at 20 feet away was 35 feet across. The concave mirror’s average field of view at 20 feet away was 10 feet across. The logical conclusion is that convex mirrors make images appear smaller than they are, but this allows you to see more in the mirror. In other words, the field of view is larger when using a convex mirror.

Review of Research

A convex mirror, fish eye mirror or separating mirror is a curved mirror in which the reflective surface bulges toward the light source. Convex mirrors reflect light outwards; therefore they are not used to focus light. Such mirrors always form a virtual image, since the focus and the center of curving are both imaginary points "inside" the mirror, which cannot be reached.
As a result, images formed by these mirrors cannot be projected on a screen, since the image is inside the mirror. A parallel beam of light diverges after reflection from a convex mirror, since the normal to the surface differs with each spot on the mirror. A concave mirror, or converging mirror, has a reflecting surface that bulges inward (away from the incident light). Concave mirrors reflect light inward to one focal point. They are used to focus light. Unlike convex mirrors, concave mirrors show different image types depending on the distance between the object and the mirror.
These mirrors are called "converging" because they tend to collect light that falls on them, refocusing parallel incoming rays toward a focus. This is because the light is reflected at different angles, since the normal to the surface differs with each spot on the mirror.

If an object is viewed through a concave mirror versus a convex mirror, then the field of view will increase. I have one control group and two experimental groups. Both of the experimental groups had 5 or more repeated trials, but one was the area viewed through a concave mirror and the other was viewed through the convex mirror.
One quick way to change the way a mirror works is to curve it. Curved mirrors come in two basic flavors: convex and concave. A convex mirror, which bulges outward, reflects at a wider angle near its edges than at its center, creating a slightly distorted image that's smaller than actual size. Convex mirrors have many uses. The smaller size of the images means that you can see more with these surfaces, hence their use in safety mirrors. (This is why your passenger side mirror says that objects are closer than they appear.) Some department stores have reportedly placed convex mirrors in their dressing rooms. Why? Slight bends at the top and bottom make you look taller and thinner. Some constants were that the mirrors had to be the same brand and size, both mirrors had to be the same distance from the object, and the same methods of measurements had to be used. The Independent variable was the concave and convex mirrors and the Dependent variable was the field of view of the two mirrors.

Procedure

The materials used included a convex mirror, a concave mirror, a digital camera, a digital measuring tape, and a field of view. The field of view was viewed backwards and the camera was used to take a picture of the area the mirror covered. The same thing was done for the other mirror. This was repeated five times for each mirror. Then the digital laser measuring tape was used to measure the area shown in the picture and the results were recorded.

Results
CONCAVE MIRRORS
CONCAVE MIRRORS

Distance from object | Avg. Size of Field of View (ft.) | 10 feet | 20 feet | 15 feet | 15 feet | 20 feet | 10 feet | 25 feet | 5 feet | CONVEX MIRRORS
CONVEX MIRRORS | | | | Distance from object | Avg. Size of Field of View (ft.) | | | 10 feet | 25 feet | 15 feet | 30 feet | 20 feet | 35 feet | 25 feet | 40 feet |

Concave Convex

Distance from Obj. (ft)
Distance from Obj. (ft)

Distance from Obj. (ft)
Distance from Obj. (ft)

Size of Field of View (ft) Size of Field of View (ft) Size of Field of View (ft) Size of Field of View (ft)

The mirrors on the sides of cars are convex; therefore when convex mirrors are used and the distance from the object is increasing, the size of the field of view will also increase. If convex mirrors are used and the field of view is increasing, the size of the field of view will decrease. It will decrease because concave mirrors have reflecting surfaces that bulge inward. Conclusion

The conclusion that must be drawn is that the hypothesis was proven incorrect. Concave mirrors made the objects flip upside down sometimes, but whether it made the object larger or smaller depended on the distance the object was held from the mirror. A convex mirror, which bulges outward, reflects at a wider angle near its edges than at its center, creating a slightly distorted image that's smaller than actual size. Convex mirrors have many uses. The smaller size of the images means that you can see more with these surfaces, hence their use in safety mirrors. This is why your passenger side mirror says that objects are closer than they appear.