Page 170 - NCERT Science Class 10 English Medium

n Eyes must be removed within 4-6 hours after death. Inform the nearest eye bank
immediately.
n The eye bank team will remove the eyes at the home of the deceased or at a hospital.
n Eye removal takes only 10-15 minutes. It is a simple process and does not lead to
any disfigurement.
n 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.

THROUGH
LIGHT
OF
A
10.3 REFRACTION
10.3 REFRACTION OF LIGHT THROUGH A PRISMREFRACTION OF LIGHT THROUGH A PRISM
10.3 REFRACTION OF LIGHT THROUGH A PRISM
PRISM
10.3 REFRACTION OF LIGHT THROUGH A PRISM
10.3
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.
10.1
Activity 10.110.1
Activity
Activity 10.1
Activity 10.1
Activity
n Fix a sheet of white paper on a drawing board using drawing pins.
n 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.
n Draw a straight line PE inclined to one of the refracting surfaces,
say AB, of the prism.
n Fix two pins, say at points P and Q, on the line PE as shown in
Fig. 10.4.
n Look for the images of the pins, fixed at P and Q, through the
other face AC.
n 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.
n Remove the pins and the glass prism.
n 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.
n Draw perpendiculars to the refracting surfaces AB and AC of the
prism at points E and F, respectively.
n 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

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