physics
posted by Daniel .
A convex mirror in an amusement park has a radius of curvature of 3.00m. A man stands in front of the mirror so that his image is half as tall as his actual height. At what distance must the man focus his eyes in order to see his image?
I calculated the focal length using f=(.5)(3.00m)
then I tried to find the image distance(di) but I get stuck.
What am I supposed to be doing here?

You have correctly determined that f = 1.5 m for this mirror. From the magnification of 1/2, and the fact that it is a virtual image, you also know that
di/do = 1/2.
Therefore 1/di + 1/do = 1/di  1/2di =
1/2di = 1/f = 2/3
Therefore di = 3/2 m and do = 3 m
Since the observer is the "object" and his image is on the other side of the mirror, he must focus his eyes 4.5 meters away.
Check my thinking. I could have made a mistake somewhere 
you kind of just droped 1/di there. where did it go?
I just don't get how you got to:
1/di  1/2di
and then you went from
1/di  1/2di = 1/2di.....you just droped 1/di. That doesnt make any since. 
1/di could also be written 2/2di then if you take away 1/2di you are left with 1/2di. It's like saying 1 minus 1/2 equals 1/2
Respond to this Question
Similar Questions

Physics  Mirrors & Lenses
When standing 1.25 m in front of an amusement park mirror, you notice that your image is three times taller. What is the radius of curvature of the mirror? 
College Physics
An amusement park mirror shows anyone who stands 2.5 meters in front of it an upright image two times the person's height. What is the mirror's radius of curvature? 
physics
A concave spherical mirror has a radius of curvature 15 cm. A 1 cm tall bulb is placed in front of the mirror such that its image is formed 10 cm in front of the mirror. If you measure distance from the optic center of the mirror, … 
physics 
A concave spherical mirror has a radius of curvature 15 cm. A 1 cm tall bulb is placed in front of the mirror such that its image is formed 10 cm in front of the mirror. If you measure distance from the optic center of the mirror, … 
Physics
A convex mirror has a radius of curvature of 36.0 cm. When a 5.60 cm tall object is placed in front of the mirror, the magnification is 0.250. (a) What is the height of the image? 
Physics
A convex mirror forms an image of height of 2.4 cm, If the radius of curvature of thr mirror is 40 cm, find the heihgt and distance of the object from the mirror. 
physics
A 4.5 cm tall object is placed 20 cm in front of a spherical mirror. It is desired to produce a virtual image that is upright and 3.5 cm tall. (a) What type of mirror should be used? 
physics
An object is placed in front of a convex mirror with a 22.6cm radius of curvature. A virtual image half the size of the object is formed. At what distance is the object from the mirror? 
physics
A person stands in front of a mirror at an amusement park. the person is left of a mirror. the mirror shows an upright image of the person that seems to be 4.0 meters behind the mirror. assume the image is 3.5 times the person's height. … 
Optics
An object, 12 cm tall, is placed 8.0 cm in front of a convex mirror with a radius of curvature of 7.0 cm. Use the mirror formula to determine the position and height of the image.