Physics for Information Science: Unit IV: Optical Properties of Materials
Dome Shaped LED
Construction, Working Principle
In the planer LED, the reflection loss is more because most of the emitted light strikes the material interface at an angle greater than the critical angle.
DOME
SHAPED LED
In
the planer LED, the reflection loss is more because most of the emitted light
strikes the material interface at an angle greater than the critical angle.
Therefore they are totally internally reflected and will not come out of the
interface. Thus the light is lost.
This
loss of light due to internal reflection can be minimised by two ways. viz.,
(i) By making the 'p' material in the shape of
a hemispherical dome (Fig. 4.22). The angle at which the light strikes the
interface can be made less than the critical angle and hence the light will not
be lost by total internal reflection.
(ii)
By covering the p-n junction by a plastic medium of higher refractive index in
the shape of hemispherical dome (Fig. 4.23), the total internal reflection can
be reduced. This LED is used for commercial purpose. Hence, usually the dome
shaped hemispherical LED is prefered than planer LEDs.
Physics for Information Science: Unit IV: Optical Properties of Materials : Tag: : Construction, Working Principle - Dome Shaped LED
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Physics for Information Science
PH3256 2nd Semester CSE Dept | 2021 Regulation | 2nd Semester CSE Dept 2021 Regulation