A small mirror is attached to a vertical wall, and it hangs a distance of 1.99 m
ID: 2030388 • Letter: A
Question
A small mirror is attached to a vertical wall, and it hangs a distance of 1.99 m above the floor. The mirror is facing due east, and a ray of sunlight strikes the mirror early in the morning and then again later in the morning. The incident and reflected rays lie in a plane that is perpendicular to both the wall and the floor. Early in the morning, the reflected ray strikes the floor at a distance of 3.66 m from the base of the wall. Later on in the morning, the ray is observed to strike the floor at a distance of 1.10 m from the wall. The earth rotates at a rate of 15.0 per hour. How much time (in hours) has elapsed between the two observations
Explanation / Answer
Initial angle of incidence, theta_i = tan^-1(1.99/3.66)
= 28.5 degrees
final angle of incidence, theta_f = tan^-1(1.99/1.1)
= 61.1 degrees
anguar displacement, theta = theta_f - theta_i
= 61.1 - 28.5
= 32.6 degrees
time elapsed = theta/15 hours
= 32.6/15
= 2.17 hours <<<<<<<-------Answer
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