• Blackboard optics equipment
• Small white screen

Spherical aberration and chromatic aberration are briefly discussed. A converging lens is placed in front of a light source and parallel rays are projected onto the blackboard. These rays demonstrate both spherical and chromatic aberration. The aberrations are enhanced when the lens is replaced with a semicircular piece of plastic.

• Blackboard optics equipment
• Two converging lenses
• Light source
• Small screen
• Stands for lenses and screen

Blackboard optics is used to demonstrate how the effective focal length of a lens can be changed by adding another lens to it. Then on the lecture table, the image of a light bulb is projected through a converging lens onto a nearby screen to show sharp focus for a farsighted eye. Next, the light bulb is moved closer to the lens to blur the image and simulate farsightedness. A second converging lens is placed in front of the first lens which brings the image again into focus, thereby correcting the farsightedness.

• Two converging lenses
• Diververging lens
• Light source
• Small screen
• Stands for lenses and screen

Two converging lenese are combined to simulate a short focal length eye. On the lecture table, the image of a light bulb is projected through the combined lenses onto a nearby screen to show sharp focus for a nearsighted eye. Next, the light bulb is moved farther from the combined lenses to blur the image and simulate nearsightedness. A diverging lens is placed in front of the combined lenses which brings the image again into focus, thereby correcting the nearsightedness.

• Blackboard optics lens
• Converging lens

Astigmatism is described with the aid of a lens which is shaped with two diffenet curvatures.