Problem 25.15-Enhanced-with Feedback 20 of 59 > Galileo attempted to measure the speed of light by measuring the time elapsed between his opening a lantern and his seeing the light return from his assistant\'s lantern. The experiment is illustrated in the figure(Figure 1) You may want to review Pages 885-889) ? Part A What distance, d, must separate Galileo and his assistant in order for the human reaction time, ?t-02 s, to introduce no more than a 20 % error in the speed of light? Express your answer using two significant figures. 1? Figure Submit Request Answer Provide Feedback Next > Solution round trip distance /(expected time - 0.2 s) = 20% more than normal speed of light 2d / [(2d /c) - 0.2 ] = 1.20c 2d = 1.20c [ 2d/c - 0.2] = 2.4 d - 0.2 * 1.20 c 0.4d = 0.2 * 1.20 c d = 0.2 * 1.20c / 0.4 = 0.6c = 1.8 x 10^8 m .