Image Size in a Mirror Part A How far away does the image appear to Joe? A guy n
ID: 1500637 • Letter: I
Question
Image Size in a Mirror Part A How far away does the image appear to Joe? A guy named Joe, who is 1.6 meters tall, enters a room in which someone has pla radius of curvature R equal to 30 meters. The mirror has been cut in half, so that the axis of the mirror is at ground level. (Figure 1 As Joe enters the room, he is 5 meters in front of the mirror, but he is looking the other way, so he fails to see it. When he turns around, he is startled by his own image in the mirror ced a l large convex mirror with Express your answer in meters, to three significant figures or as a fraction 8.75 m Submit Hints My Answers Give Up Review Part Correct Part B Figure 1 of 2 What is the image height yim that Joe sees in the mirror? Express your answer in meters, to three significant figures or as a fraction Mirror 2.77 Submit Hints My Answers Give Up Review Part Incorrect; Try Again; 5 attempts remaining Joe is so startled by his image that he falls forward. (Assume that his feet stay at the same position.) Figure 2)Explanation / Answer
( a)
Here focal length is f = R /2 = 15 cm
Use lens equation,
1/f = 1/do+ 1/di
Substitute given values
1/-15 = 1/5 + 1/di
di = -3.75 m
Thus, the distance part is
5 - (- 3.75 ) = 8.75 m
---------------------------------------------------------------------------
( b)
From the definition of magnification
m - di / do = hi/ ho
This implies that
hi / ho -di / do
hi/ 1.6 3.75 / 5
Solve for image height
hi = 1.2 m
-----------------------------------------------------------------------------------
(c )
Again, use lens equation
1/f = 1/do + 1/di
Substiute numerical values and solve for image distance
1/-15 = 1/3.4 + 1/di
di = -2.77 m
In this case,
di-head - di-foot = -3.75 - ( - 2.77 )
di-head - di-foot = -0.980 meters