Editing Content :: Admin Scraper

Chapter

Content type

Position

Value

■ Eyes must be removed within 4-6 hours after death. Inform the nearest eye bank immediately. ■ The eye bank team will remove the eyes at the home of the deceased or at a hospital. ■ Eye removal takes only 10-15 minutes. It is a simple process and does not lead to any disfigurement. ■ Persons who were infected with or died because of AIDS, Hepatitis B or C, rabies, acute leukaemia, tetanus, cholera, meningitis or encephalitis cannot donate eyes. An eye bank collects, evaluates and distributes the donated eyes. All eyes donated are evaluated using strict medical standards. Those donated eyes found unsuitable for transplantation are used for valuable research and medical education. The identities of both the donor and the recipient remain confidential. One pair of eyes gives vision to up to FOUR CORNEAL BLIND PEOPLE. 10.3 REFRACTION OF LIGHT THROUGH A PRISM You have learnt how light gets refracted through a rectangular glass slab. For parallel refracting surfaces, as in a glass slab, the emergent ray is parallel to the incident ray. However, it is slightly displaced laterally. How would light get refracted through a transparent prism? Consider a triangular glass prism. It has two triangular bases and three rectangular lateral surfaces. These surfaces are inclined to each other. The angle between its two lateral faces is called the angle of the prism. Let us now do an activity to study the refraction of light through a triangular glass prism. Activity 10.1 ■ Fix a sheet of white paper on a drawing board using drawing pins. ■ Place a glass prism on it in such a way that it rests on its triangular base. Trace the outline of the prism using a pencil. ■ Draw a straight line PE inclined to one of the refracting surfaces, say AB, of the prism. ■ Fix two pins, say at points P and Q, on the line PE as shown in Fig. 10.4. ■ Look for the images of the pins, fixed at P and Q, through the other face AC. ■ Fix two more pins, at points R and S, such that the pins at R and S and the images of the pins at P and Q lie on the same straight line. ■ Remove the pins and the glass prism. ■ The line PE meets the boundary of the prism at point E (see Fig. 10.4). Similarly, join and produce the points R and S. Let these lines meet the boundary of the prism at E and F, respectively. Join E and F. ■ Draw perpendiculars to the refracting surfaces AB and AC of the prism at points E and F, respectively. ■ Mark the angle of incidence (∠i), the angle of refraction (∠r) and the angle of emergence (∠e) as shown in Fig. 10.4. The Human Eye and the Colourful World 165 Reprint 2026-27