PCS 224 Midterm: PCS224 - F2010 Midterm (Solution)
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Student number: _____________________ student section: _______________ (check your bubble sheet) . instructions: duration of the exam: 110 minutes, this is a closed book exam; pens, pencils, erasers, calculators and your ryerson id are the only allowed items on your desk. Your ryerson photo id must be on your desk at all times. Please sign here indicating you have read and understood the above instructions. Do not open the exam until you are told to do so. Then, before you start writing, verify that you do have all 11 pages (otherwise inform one of the invigilators). The weight of each multiple-choice question is 5 points: in an experiment different wavelengths of light, all able to eject photoelectrons, shine on a freshly prepared (oxide-free) zinc surface. 2. a crystal of silicon has had one atom out of every 2x108 atoms replaced with a n-type (valence 5) atom at t= 300k. Determine the density of holes in this crystal: 2. 25x105 cm-3, 1. 36x104 cm-3.
