Q4. (20 points) Light is often described in wavelength (nm) and by its energy (in ev). a. Calculate the energy in eV for light with wavelengths of 250 nm, 532 nm, 1000 nm, and 2000 nm. (5 points) b. Answer: If you had light of these 4 wavelengths incident at room temperature on: borosilicate glass with a bandgap of 4.28 eV, an Indium Gallium Nitride (InGaN) wafer with direct bandgap of 2 eV, a Germanium wafer with an indirect bandgap of 0.66 ev, and a metal which has no bandgap, which of these 4 lights would be transmitted in each case? (5 points) c. Answer: For the case of InGaN, what color light will be emitted from the wafer in each case of incident light wavelengths specified in (a)? For each case, calculate the wavelength of this emitted light. (5 points) d. You shine a light of wavelength v1 on a sample of InGaN and experimentally obtain an absorption coefficient a1. Then you shine a light of wavelength v2 on that same sample and experimentally obtain an absorption coefficient a2. Given the relationship a = A* ( hv - Eg) g)"for direct bandgap semiconductors (where A* is an arbitrary material- dependent coefficient), explain how you can calculate the bandgap of InGaN by extrapolation. You may find it convenient to sketch how this extrapolation might work to assist your explanation. (5 points)