COMEDK · Physics · 30. Semiconductors
What is the minimum band-gap of the LED diode?
- A \(1.5 \mathrm{eV}\)
- B \(1.6 \mathrm{eV}\)
- C \(1.8 \mathrm{eV}\)
- D \(0.8 \mathrm{eV}\)
Answer & Solution
Correct Answer
(C) \(1.8 \mathrm{eV}\)
Step-by-step Solution
Detailed explanation
For an LED to emit visible light, the photon energy must correspond to the visible spectrum (400 nm to 700 nm). Minimum band-gap corresponds to maximum wavelength (700 nm, red light):…
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- A coil of wire of a certain radius has 100 turns and a self inductance of \(15 \mathrm{mH}\). The self inductance of a second similar coil of 500 turns will beCOMEDK 2020 Hard
- The first emission of hydrogen atomic spectrum in Lyman series appears at a wavelength ofCOMEDK 2023 Medium
- Vectors \(\mathbf{A}, \mathbf{B}\) and \(\mathbf{C}\) are such that \(\mathbf{A} \cdot \mathbf{B}=0\) and \(\mathbf{A} \cdot \mathbf{C}=0\), then the vector parallel to \(\mathbf{A}\) isCOMEDK 2013 Easy
- Weight of the body on the surface of the earth is 64 N . What will be the gravitational force acting on it, if it is taken up to a height equal to \(\left(\dfrac{1}{3}\right)^{r d}\) of the radius of the earth from the earth's surface?COMEDK 2025 Medium
- A transformer has 400 turns in its primary winding and 800 turns in its secondary winding. The primary voltage is \(20 \mathrm{~V}\) and the load in the secondary is 4 ohm. The current in the primary, assuming it to be an ideal transformer, isCOMEDK 2024 Medium
- If a change in current of \(0.01 \mathrm{~A}\) in one coil produces a change in magnetic flux of \(2 \times 10^{-2}\) weber in another coil, then the mutual inductance between coils isCOMEDK 2014 Easy
More PYQs from COMEDK
- Identify the two statements which are incorrect regarding Corrosion of Iron.
A. During electrical protection of underground Iron pipes from corrosion the connected Mg plate undergoes reduction.
B. At the Cathodic area on Iron the reaction occurring is \(4 \mathrm{H}^{+}+\mathrm{O}_2+4 \mathrm{e} \rightarrow 2 \mathrm{H}_2 \mathrm{O}\)
C. Rust formed \(\mathrm{Fe}_2 \mathrm{O}_3 . \mathrm{xH}_2 \mathrm{O}\) is an acidic oxide.
D. The \(\mathrm{H}^{+}\)ions are obtained from water containing dissolved gases like \(\mathrm{SO}_2, \mathrm{NO}_2\) or \(\mathrm{CO}_2\).COMEDK 2025 Medium - \(\text { The value of } \int \dfrac{1}{x+\sqrt{x-1}} d x \text { is }\)COMEDK 2024 Hard
- If \(2\sin\theta = \left(x + \dfrac{1}{x}\right)\), then \(\sin 3\theta + \dfrac{1}{2}\left(x^3 + \dfrac{1}{x^3}\right) =\)COMEDK 2026 Medium
- A cone whose height is always equal to its diameter is increasing in volume at the rate of \(40 \mathrm{~cm}^3 / \mathrm{sec}\). The rate at which the radius is increasing when its circular base is \(1 \mathrm{~m}^2\) isCOMEDK 2025 Medium
- The angle between lines \(\sqrt{3} x+y=1\) and \(x+\sqrt{3} y=1\) isCOMEDK 2014 Medium
- The area of the triangle whose vertices are \((-2, a)(2,-6)\) and \((5,4)\) is 35 sq units then the value of '\(\mathrm{a}\)' isCOMEDK 2024 Medium