Page 142 - Science Class 07

eye-hole. Several pieces of coloured beads of
Regular Reflection
Irregular Reflec on
When a parallel beam of light strikes a rough
surface and bounces back in different
direc on, then such kind of reflec on is called
irregular reflec on. Concrete floor, water,
stone, etc. cause irregular reflec on.
Irregular Reflection
KALEIDOSCOPE
A kaleidoscope is an op cal device that is
cylindrical in shape. It is about 25 cen meters
long and 5 to 8 cen meters across. Both its
ends are closed but one of them has an eye- 45° with the axis of the tube. These mirrors act
hole used for looking through into the device.
Kaleidoscope
This device works on the principle of mul ple
images created by mirrors inclined to each
other. Two mirrors run through the en re
cylindrical tube. Also, there are two plates
—one of smooth glass while the other of
ground glass. The smooth plate is close to the
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glass are placed between the two plates. The
image of these beads are formed in the
mirrors. When we turn the device, the pa erns
of these head-images change. This device was
developed by Sir David Brewster in 1917 for the
designers to guide them for crea ng new
pa erns of rug, wall-paper and fabrics.
A Pa ern Made by Kaleidoscope
PERISCOPE
A periscope is an op cal device that enables a
viewer to observe objects from a distance and
also when the vision is blocked. It consists of a
long tube that has a plane reflec ng mirror at it
either end. The mirrors are fixed in a parallel
posi on and either of them makes an angle of
as telescope and enlarge the objects to be
seen.
The light that the object to be seen reflect
strikes the mirror fi ed at the top of the device.
It further reflects this light to the mirror at the
bo om. And the bo om mirror reflects it to
the eyes of the viewer who can see it clearly.
Periscopes are fi ed to submarines that move
under water. They help the object at the water
surface to be seen easily.
Periscopes are fi ed to ba le-tanks that are
kept closed to be safe against chemical
Science-7