Advertisements
Advertisements
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
Advertisements
उत्तर
the band gap of the material of semiconductor
APPEARS IN
संबंधित प्रश्न
With the help of a neat circuit diagram, explain the working of a photodiode.
Meeta's father was driving her to school. At the traffic signal, she noticed that each traffic light was made of many tiny lights instead of a single bulb. When Meeta asked this question to her father, he explained the reason for this.
Answer the following questions based on above information:
(i) What were the values displayed by Meeta and her father?
(ii) What answer did Meeta's father give?
(iii) What are the tiny lights in traffic signals called and how do these operate?
How is a Zener diode fabricated?
Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.
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?
With what considerations in view, a photodiode is fabricated? State its working with the help of a suitable diagram.
Even though the current in the forward bias is known to be more than in the reverse bias, yet the photodiode works in reverse bias. What is the reason?
Using the necessary circuit diagrams, show how the V-I characteristics of a p-n junction are obtained in
Forward biasing
How are these characteristics made use of in rectification?
The width of depletion region of p-n junction diode is _______.
(A) 0.5 nm to 1 nm
(B) 5 nm to 10 nm
(C) 50 nm to 500 nm
(D) 500 nm to 1000 nm
State its any ‘two’ uses of 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
Show the output waveforms (Y) for the following inputs A and B of (i) OR gate (ii) NAND gate ?
Describe briefly, with the help of a diagram, the role of the two important processes involved in the formation of a p-n junction.
How does a light emitting diode (LED) work? Give two advantages of LED’s over the conventional incandescent lamps.
Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?
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 the 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?
With reference to Semiconductor Physics,
Name the process that causes depletion region in a p-n junction.
What is the magnitude of the potential barrier across a Ge p-n junction?
For LED's to emit light in visible region of electromagnetic light, it should have energy band gap in the range of:
In Figure, assuming the diodes to be ideal ______.
Read the following paragraph and answer the questions.
|
LED is a heavily doped P-N junction which under forward bias emits spontaneous radiation. When it is forward-biased, due to recombination of holes and electrons at the junction, energy is released in the form of photons. In the case of Si and Ge diode, the energy released in recombination lies in the infrared region. LEDs that can emit red, yellow, orange, green and blue light are commercially available. The semiconductor used for fabrication of visible LEDs must at least have a band gap of 1.8 eV. The compound semiconductor Gallium Arsenide – Phosphide is used for making LEDs of different colours.
|
- Why are LEDs made of compound semiconductor and not of elemental semiconductors?
- What should be the order of bandgap of an LED, if it is required to emit light in the visible range?
- A student connects the blue coloured LED as shown in the figure. The LED did not glow when switch S is closed. Explain why?
OR
iii. Draw V-I characteristic of a p-n junction diode in
(i) forward bias and (ii) reverse bias
Draw the circuit diagram of an illuminated photodiode and its I-V characteristics.
The value of power dissipated across the Zener diode (Vz = 15 V) connected in the circuit as shown in the figure is x × 10–1 watt. The value of x, to the nearest integer, is ______.
What energy conversion takes place in a solar cell?
