Silicon (Si) is used for night-vision infrared optics. Si is transparent to infrared radiation because the energy gap of Si is 1.1 eV. What is the longest wavelength photon that has sufficient energy to excite a valence electron across the energy gap?
What will be an ideal response?
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Most SETI searches are done at
A) X-ray wavelengths. B) visual wavelengths. C) infrared wavelengths. D) radio wavelengths. E) gamma wavelengths.
Angular Momentum: Initially, a small 2.0-kg rock is whirling at the end of a very thin string in a circular path of radius 0.75 m on a horizontal frictionless surface, as shown in the figure. The initial tangential speed of the rock was 5.0 m/s. The string has been slowly winding around a vertical rod, and a few seconds later the length of the string has shortened to 0.25 m. What is the instantaneous speed of the mass at the moment the string reaches a length of 0.25 m?
A. 3.9 m/s B. 9.3 m/s C. 15 m/s D. 225 m/s E. 75 m/s
Atoms in crystals are typically separated by distances of 0.10 nm. What KE must an electron have, in eV, in order to have a wavelength of 0.10 nm?
What will be an ideal response?
Almost all molecules in space are based on what element? Why?
What will be an ideal response?