PHYS 221L Midterm, Fall 2009

PHYS 221L – Midterm - December 2009 1. In the DMM experiment, 1% -tolerance resistors were used to construct a 20V-full-scale voltmeter using a 3 ½ digit DVM. The DVM has a rated accuracy of 1%. a) Draw the diagram of the voltmeter. b) What is the resolution of the constructed voltmeter? c) What is the probable error of your voltmeter? 2. On student measures a quantity N times and reports the most probable value and error. A second student wants to continue the measurement and decrease the probable error by a factor of 2. How many more measurement should the second students make? And how should he combine his results with those of the first student? 3. An Oscilloscope can be used to measure the frequency of a sine voltage; the rated time- base accuracy is 2%. Explain in detail how you would arrange your display in order to obtain the best possible value. In this case, what is the probable error. Indicate what assumptions you are making. 4. In the spectroscopy experiment, you observe the following lines of mercury at the specified angles. If no lines are observed below 15 degrees, use ALL the lines to calculate the spacing of the grating. Wavelength(nm) Angle(deg) Violet (405) 15.0, 54.5 Blue (436) 16.2, 35.1 Green (546) 46.9 Yellow (577) 22.7, 50.9 5. In the polarization experiment, you make the following measurement: Θ in cadence I(max) I(min) 75 8.4 2.8 70 6.8 1.2 65 3.4 0.40 60 4.9 0.20 55 4.2 0.10 50 3.3 0.12 45 2.3 0.13 40 1.6 0.32 Calculate the index of refraction of the prism.