12th Class Physics Sample Paper Physics Sample Paper-1

  • question_answer
    Name the device which is used in cell phones which produces light in its display. Write and explain the principle on which this device is based.


    Light is produced in cell phone's display with the help of the device known as LED (Light Emitting Diode). It is heavily doped forward biased p-n junction diode which converts electrical energy into light energy. When p-n junction is forward biased, electrons and holes move towards opposite sides of junction through it. Therefore, there are excess minority carriers on the either side of the junction boundary, recombines with majority carriers near the junction. On recombination of electrons and holes, the energy is given out in the form of heat and light.

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