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Practical work in physics Worksheet 2 Measurements and errors 1. Refractive index of a material, n = (sin i)/ (sin r) In an experiment to find the refractive index of glass, the following measurements were taken: The angle of incidence in air, i = 480 The angle of refraction in glass, r= 300 The angles were measured with a protractor that has smallest division of 1 degree. a. What is the precision of the protractor? b. Find the refractive index of glass c. Find the percentage uncertainties in i. the angle of incidence ii. the angle of refraction iii. the refractive index d. What is the uncertainty in refractive index of glass? CN 23 FEB 12 2. Period of a simple pendulum, T = 2(L/g)1/2 a. Make g the subject of the formula b. What is meant by a fiducial mark? c. State with a reason your choice of fiducial mark in measuring the period of oscillation of a pendulum. d. In an experiment to find the acceleration due to gravity, the following results were obtained: Length of pendulum, L = 72 cm (to the nearest mm) The time for 10 oscillations: 17.1, 17.0, 17.5, 17.3 and 17.3 sec (to the nearest 0.1 sec) Find i. The mean value of the time period T ii. the range of T iii. the uncertainty in T iv. the percentage uncertainties in T, in L and in g v. the value of g vi. the uncertainty in g CN 23 FEB 12