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1. What is photoelectric effect?
Emission of electrons from a material when electromagnetic radiation (light) is in incident on it. It was discovered by Albert Einstein.
2. What is LDR?
Light dependent resistor. It convert light energy into electrical energy.
3. Working of LDR?
Photocell is a resistor that changes resistance depending on the amount of light incident on it. It operates on semiconductor photo conductivity. The passive component is a resistor whose resistance value decreases when intensity of light increases.
4. Why inert gases are filled photocell?
Inert gases like neon, argon are filled inside the cell to increase the ionisation and thereby increasing the photoelectric current.
5. What is stopping potential?
It’s the voltage difference required to stop the ejection of electrons and stop their movement between the plates. Stopping potential is negative. It depend on the frequency of incident radiation but not on its intensity.
6. For which colour stopping potential is more?
Blue, since it’s has minimum wavelength.
7. Define threshold frequency?
Minimum frequency of incident radiation below which photoelectric effect is not possible.
8. What is work function?
It’s the minimum energy required to remove the electron from the material.
9. Application of photocell?
Solar cells, Buglar alarm, calculators, camera, lens, etc.
10. Why photodiode is reverse biased?
Photodiode is reverse biased because it causes the potential across depletion region to increase and the width of depletion region increases.
11. Define LED?
Light emitting diode; it converts electrical energy into light energy.
12. Name the device which is the combination of LED and photocell.
Opto coupler