Q1. Potassium iodide has an interplanar spacing of d = 0.296 nm. A monochromatic X-ray beam shows first-order diffraction maximum while the grazing angle is 7.8°. Compute the X-ray wavelength λ.
Q2. The longest "string" (a thick metal wire) on a particular piano is 3.0 m long and has a tension of 300.0 N. It vibrates with a basic frequency of 27.5 Hz. What is the total mass of the wire?