LED — Prelims Questions

An LED is constructed from a p-n junction based on a certain semiconductor material. The energy band gap of this material is $1.9,\text{eV}$. What is the approximate wavelength of the light emitted by this LED? (Given: Planck's constant $h = 6.63 \times 10^{-34},\text{J}cdot\text{s}$, speed of light $c = 3 \times 10^8,\text{m/s}$, $1,\text{eV} = 1.6 \times 10^{-19},\text{J}$)

Which of the following semiconductor materials is typically used for producing blue LEDs?

An LED is always connected in series with a resistor. The primary reason for this is to:

Which of the following statements about LEDs is INCORRECT?

A green LED has a bandgap energy of approximately $2.25,\text{eV}$. What is the frequency of the emitted photons? (Given: Planck's constant $h = 6.63 \times 10^{-34},\text{J}cdot\text{s}$, $1,\text{eV} = 1.6 \times 10^{-19},\text{J}$)

Which of the following is NOT an advantage of LEDs over traditional incandescent bulbs?