NEET Physics: LED and photodiode Practice Questions
15 free multiple-choice questions on LED and photodiode (Semiconductors) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. The primary function of a photodiode is to convert incident light energy into which form of electrical energy?
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Correct answer: B — Electrical energy
A photodiode operates based on the photoelectric effect, where incident photons are absorbed and generate electron-hole pairs, converting the light energy into electrical current.
Q2. The resistance of a photodiode is generally considered to be:
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Correct answer: C — Inversely proportional to the incident light intensity
When operating in the photoconductive mode, the resistance of the photodiode decreases as the incident light intensity increases because the generated photocurrent increases.
Q3. A photodiode primarily functions as a light sensor by converting incident light energy into what form of energy?
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Correct answer: C — Electrical energy
A photodiode absorbs photons, which generate electron-hole pairs, resulting in a measurable electrical current (photocurrent).
Q4. For an LED to emit visible light, the energy gap of the semiconductor material must be related to the energy of the emitted photon. Which principle governs this relationship?
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Correct answer: B — Band Gap Energy
The energy of the emitted photon is directly related to the energy band gap (E_g) of the semiconductor material, as Eₚₕₒₜₒₙ ≈ E_g.
Q5. For an LED to operate, the forward bias voltage must be applied across the junction, which results in:
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Correct answer: D — Increased electron flow and light emission
Applying forward bias increases the concentration of minority carriers (electrons and holes) in the depletion region, leading to higher recombination rates and the emission of light.
Q6. A photodiode functions as a light-to-current converter. If the intensity of incident light increases, what happens to the output current generated by the photodiode, assuming constant bias?
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Correct answer: D — The output current increases
The photocurrent generated is directly proportional to the number of photons absorbed, hence increased light intensity leads to increased photocurrent.
Q7. Which component is primarily responsible for converting incident photons into electrical current in a photodiode?
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Correct answer: C — Photoconductor
Photodiodes operate based on the photovoltaic effect, where incident light generates electron-hole pairs, which results in a measurable photocurrent.
Q8. The light emission characteristics of an LED are primarily determined by the material's:
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Correct answer: B — Band Gap Energy
The color and wavelength of light emitted by an LED are directly related to the energy difference between the conduction band and the valence band, known as the band gap energy of the semiconductor material.
Q9. When a p-n junction diode is operated in reverse bias, what is the primary effect observed in the depletion region?
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Correct answer: D — The depletion region widens
In reverse bias, the applied voltage increases the potential barrier across the depletion region, causing the depletion region to widen.
Q10. Which material is commonly used for the base material in Light Emitting Diodes (LEDs) due to its efficient light emission properties?
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Correct answer: A — Gallium Arsenide (GaAs)
Gallium Arsenide (GaAs) and related compounds are often preferred for high-efficiency light emission in LEDs due to their suitable band gap and material properties.
Q11. The material used to construct both LEDs and photodiodes is primarily based on which type of semiconductor?
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Correct answer: D — Extrinsic semiconductor
LEDs and photodiodes are built using semiconductor materials (like GaAs or Si) which are extrinsic semiconductors, typically doped to form P-N junctions.
Q12. In an LED, the color of the emitted light is primarily determined by the energy difference between the conduction band and the valence band of the semiconductor material. This difference is known as the:
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Correct answer: C — Band gap energy
The energy gap between the conduction band and the valence band (the band gap energy) dictates the energy of the photons emitted when electrons transition across this gap.
Q13. The mechanism by which a photodiode generates a current in response to light is known as:
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Correct answer: B — Photoelectric effect
The detection mechanism in a photodiode relies on the photoelectric effect, where incident photons strike the semiconductor material and liberate charge carriers, thus generating a measurable photocurrent.
Q14. Which type of semiconductor material is commonly used as the base material for manufacturing high-efficiency blue LEDs?
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Correct answer: B — Indium Gallium Nitride (InGaN)
Indium Gallium Nitride (InGaN) is the most widely used material for high-efficiency blue and green LEDs due to its suitable band gap and high luminescence properties.
Q15. In an LED, the light emission occurs primarily due to the recombination of which pair of charge carriers in the semiconductor material?
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Correct answer: A — Electrons and holes
Light emission in LEDs is the result of electron-hole recombination across the band gap, which releases energy in the form of photons.
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