Experiment 9: Concave and Convex Mirrors

Objective:

The purpose of this experiment is to study the properties of a concave and convex mirror through the images formed by them. In this experiment, a plane mirror, a convex mirror, and a concave mirror are used. The image characteristics are observed and light ray diagrams are constructed.

 

Figure 1: plane mirror: the image is the same as the object

Observation:

Part A: Convex Mirror

Figure 2: Convex mirror: the image is upright but smaller than the object

For the convex mirror, the image appears to be smaller than the object. It is upright and located further than the position of the mirror and object. When the object is moved closer to the mirror, the image appears closer. When the object is moved away from the mirror, the image appears further.

The ray diagram

Ho (cm)	Hi(cm)	Do(cm)	Di(cm)
3.1± 0.05cm	0.8± 0.05cm	5.9± 0.05cm	-2.2± 0.05cm

M=hi/ho

  =0.8/3.1

  =0.258±0.0167 cm

M=-di/do

  =2.2/5.9

  =0.373±0.00904cm

Avg=0.3155±0.0129cm

Part B: Concave Mirror

 

Figure 3: Concave mirror: the image is inverted.

 

For the concave mirror, the image appears to be larger than the object. It is inverted and located closer than the position of the mirror and object. When the object is moved closer to the mirror, the image appears larger and larger, and then it becomes upright. When the object is moved away from the mirror, the image appears inverted, further and smaller.

Ray diagram

Ho (cm)	Hi(cm)	Do(cm)	Di(cm)
3.1± 0.05cm	-0.8± 0.05cm	11.6± 0.05cm	2.3± 0.05cm

M=hi/ho

  =-0.8/3.1

  =-0.258±0.0167cm

M=-di/do

  =2.3/11.6

  =-0.198±0.0108cm

Avg=-0.228±0.0138cm

Conclusion:

The purpose of this experiment is to study the properties of different kinds of mirrors. For convex mirror, from the ray diagram, it is clearly shown that the image is formed on the other side of the object. So, the image is real. The observation agreed with the light ray sketch. In the light ray diagram, the image is smaller than the object and is erect. This matches the observation. For the concave mirror, from the ray diagram, it is clearly shown that the image is formed on the same side of the object. So, the image is virtual. The image is observed to be inverted and larger than the size of the object. However, if the object moves closer and passes the focal point, the image becomes upright.