Consider a single crystal of an insulator with a band gap of 3.5 eV.   What colors of visible light will this crystal transmit?

Suppose you measured a spectrum of a laser source which peaks at a wavelength of 810 nm. Find the energy (in eV) associated with this wavelength. From the LED spectrum data you want to find the width of the peak at half the height of the peak. The wavelengths at which the intensity is half of its peak value are 630 nm and 666 nm respectively. Using these wavelengths determine the width of the peak in units of energy (eV). From the N2 spectrum data you noted two prominent peaks at wavelengths 330 nm and 350 nm. Determine the energy associated with each peak. The larger energy represents the energy difference between the vibrational ground states of two molecular orbitals (denoted by C’IIu and B³IIL). The smaller one represents the energy difference between the vibrational ground state of the C'II, orbital and first excited vibrational state of B³II.. The difference between these energies represents the energy difference between the ground and first excited vibrational levels. Find this…

A wire loop 22 cm high is dipped in a soap solution (n = 1.33) and then held vertically. It produces a film whose thickness varies from essentially zero at the top to 1.024 μm at the bottom. The film is illuminated with 517 nm light. How far down the loop (as measured from the top) does the bright band number 3 appear?

Gallium arsenide (GaAS) used to produce an LED has an energy band gap of 1.47 eV. Determine the wavelength of electromagnetic radiation that is emitted from this LED. In what region of the electromagnetic spectrum does this wavelength fall? If the emitted radiation falls within the visible spectrum, what color is it?

Silicon nitride is widely used as an antireflection material for silicon solar cells. Explain the reason.

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