Exams › JEE Main › Physics
A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is 1.42 eV. The wavelength of light emitted from the LED is:
- 650 nm
- 1243 nm
- 875 nm
- 1400 nm
Correct answer: 875 nm
Solution
The wavelength of light emitted by a semiconductor can be calculated using the energy-band gap relation, where the wavelength is inversely proportional to the energy. Given the band gap of GaAs is 1.42 eV, the corresponding wavelength is approximately 875 nm, which falls within the infrared region of the spectrum.
Related JEE Main Physics questions
- For a diode, the current–voltage relation is I = (e^(1000V/T) - 1) mA, where V is the applied voltage in volts and T is the temperature in kelvin. If the current is 5 mA at 300 K and the voltage measurement has an uncertainty of ±0.01 V, what is the resulting error in the current (in mA)?
- A common-emitter amplifier has a current gain of 62. Its collector resistance is 5 kΩ and its input resistance is 500 Ω. If the applied input voltage is 0.01 V, what is the output voltage?
- A half-wave rectifier employing a p-n junction diode is fed with an AC voltage of peak value 25 V and frequency 50 Hz. The circuit has no filter, and the load resistance is 1000 Ω. If the diode’s forward resistance R_f is 10 Ω, what is the rectification efficiency in percent?
- At 27°C, germanium has an intrinsic conductivity of 2.13 mho m−1. If the electron and hole mobilities are 0.38 m2V−1s−1 and 0.18 m2V−1s−1, respectively, what is the charge-carrier concentration?
- A transistor in good condition has its three terminals labeled P, Q, and R. When checked with a multimeter, there is no conduction between P and Q. However, if the negative lead of the meter is connected to R and the positive lead is connected to either P or Q, the meter shows some resistance. What can be concluded about the transistor?
- At 300 K, intrinsic silicon has a hole concentration of 7 × 10¹⁵ m⁻³. If antimony is introduced into silicon at the rate of 1 atom per 10⁷ silicon atoms, and only one-half of the impurity atoms supply electrons to the conduction band, by what factor does the charge-carrier concentration rise because of doping? Take the number of silicon atoms in 1 m³ to be 5 × 10²⁸.
⚔️ Practice JEE Main Physics free + battle 1v1 →