Medicine Chapter 2: Vision

Chapter Challenge
A medical technology company is exploring the possibility of becoming active in vision technology. Helping people to see better may prove to be very profitable and serves humanity. Students are challenged to write a preliminary report for the company that will help them decide whether to invest any time and labor in new vision technologies.

Chapter Summary
To gain knowledge and understanding of physics principles necessary to meet this challenge, students work collaboratively on activities in which they explore concepts of light waves and lenses, and then apply this to focal length. These experiences engage students in the content identified in the National Science Education Standards.

Activity Summaries

Physics Principles

Activity One: The Eye

Using a model of the eye and glasses that simulate vision with cataracts, students are introduced to focal length and how a lens forms images. Further exploring with convex lenses enables comparing the image to the object under different light conditions and distances.

• Images formed by convex lenses
• Image distance
• Focal length

Activity Two: How Images Are Made: Pinholes

Students learn how to obtain images of objects with lights and pinholes. After exploring how images change when the distance of the lamp to the pinhole is changed, they predict size and location of images from given information. Finally, they apply the concepts learned to design and make simple glasses.

• Image formation
• Ray optics

Activity Three: Refraction

After observing and measuring how water refracts light, students use ratios to calculate angles of incidence and refraction. Refraction of light through water is connected to refraction through a lens.

• Refraction of light
• Index of refraction

Activity Four: How Images Are Made: Converging Lenses

Investigating with convex lenses enables students to learn to draw ray diagrams to show images formed by converging lenses and that images can be larger or smaller than the object.

• Refraction of light
• Convex lenses
• Focal length

Activity Five: Accommodation

Lenses with different focal lengths are used to introduce how the lens in the eye can change its thickness to accommodate the distance of the object. This is then related to visual problems of near and farsightedness.

• Focal length
• Visual acuity

Activity Six: How Images Are Made: Diverging Lenses

Students explore concave lenses to learn how diverging lenses can work with converging lenses to create longer focal lengths.

• Light waves
• Diverging lenses

Activity Seven: Corrective Lenses

The Snellen chart and ray diagrams that illustrate how a nearsighted and farsighted eye must bend light waves are used to connect investigations with lenses back to the chapter challenge. Astigmatism and contact lenses are also introduced in this activity.

• Converging lenses
• Light waves
• Visual acuity

Activity Eight: The Retina

Students measure their own field of vision and read to learn more about how the eye is able to bend light waves to form images and "see" in more than a straight line.

• The human eye
• Peripheral vision
• Corrective lenses

Activity Nine: Visual Acuity

After testing their own visual acuity, they read to learn more about the physics behind the workings of the eye and how the eye adapts to different levels of
light intensity.

• Rod and cone cells in the eye
• Object and image separation