A reflecting, spherical Christmas tree ornament has a diameter of 7.0 cm. A child looks at the ornament from a distance of 16 cm. 


Where is the image located?

cmoore  Mar 13, 2018

2+0 Answers


This is a convex mirror.   The focal point is MIDWAY betwen the center of curvature and the lens surface and is NEGATIVE

So for this mirror  f = -1.75  (1/2 of the RADIUS)    It will produce a virtual image on the same side as the focal point (opposite the side of the OBJECT ....the child's face) so the distance result will be negative thusly:


1/f  =  1/do + 1/di          do = distance to the object = 16cm    f = - 1.75     solve for di


-1/1.75 = 1/16 + 1/di

-1/1.75 - 1/16 = 1/di

di = - 1.58 cm

ElectricPavlov  Mar 14, 2018

Thank you!

cmoore  Mar 14, 2018

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