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प्रश्न
How does a light emitting diode (LED) work? Give two advantages of LED’s over the conventional incandescent lamps.
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उत्तर
When we apply sufficient voltage to LED, electron move across the junction into the p-region and get attracted to the holes there. Thus, electrons and holes recombine. During each recombination, electric potential energy is converted into electromagnetic energy and a photon of light with a characteristic frequency is emitted, this is how LED works.
Advantage of LEDs over incandescent lamps
(1) Since LEDs do not have a filament that can burn out, they last longer.
(2) They do not get hot during use.
संबंधित प्रश्न
Colour of light emitted by LED depends upon__________________ .
- its forward bias
- its reverse bias
- the band gap of the material of semiconductor
- its size
If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is(ii) reveres biased?
Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to (Eg)C, (Eg)Si and (Eg)Ge. Which of the following statements is true?
A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm?
Describe, with the help of a circuit diagram, the working of a photodiode.
Sunil and his parents were travelling to their village in their car. On the way his mother noticed some grey coloured panels installed on the roof of a low building. She enquired from Sunil what those panels were and Sunil told his mother that those were solar panels.
(a) What were the values displayed by Sunil and his mother? State one value for each.
(b) In what way would the use of solar panels prove to be very useful?
(c) Name the semiconductor device used in solar panels. Briefly explain with the help of a diagram, how this device works
Briefly explain its working. Draw its V - I characteristics for two different intensities of illumination ?
Explain the formation of depletion layer and potential barrier in a p−n junction.
Write the important considerations which are to be taken into account while fabricating a p-n junction diode to be used as a Light Emitting Diode (LED). What should be the order of band gap of an LED, if it is required to emit light in the visible range? Draw a circuit diagram and explain its action.
What is a solar cell?
