A convex spherical mirror of focal length 15.0 cm is to form an image 9.00 cm from the mirror. Where will the object be placed?
2 answers
A man standing 1.25 m in front of a shaving mirror produces an inverted image 25.0 cm in front of it. How close to the mirror should he stand if he wants to form an upright image of his chin that is twice the actual size of his chin?
You have two completely different questions here. I will answer the second of them.
Use the information on where the inverted (real) image forms to get the focal length of the mirror.
1/125 + 1/25 = 1/f = 6/125
f = 125/6 = 20.83 cm
For the upright image with a magnification of 2, use the same focal length but use di/do = -2 to solve for do
1/do + 1/di = 1/do - 1/(2 do) = 1/20.83
1/(2 do) = 1/20.83
do = 10.42 cm
Use the information on where the inverted (real) image forms to get the focal length of the mirror.
1/125 + 1/25 = 1/f = 6/125
f = 125/6 = 20.83 cm
For the upright image with a magnification of 2, use the same focal length but use di/do = -2 to solve for do
1/do + 1/di = 1/do - 1/(2 do) = 1/20.83
1/(2 do) = 1/20.83
do = 10.42 cm
2 answers