A mirror with a focal length -25 cm has a 4.0 cm tall object placed 100 cm in front of it. What is the height of the image?
A)0.8 cm
B)20 cm
C)4.0 cm
D)-0.8 cm
E)-20 cm

Question

Quizplus · Accepted Answer

The image height is given by the thin lens equation:1/f = 1/do + 1/diwhere f is the focal length, do is the object distance, and di is the image distance.Substituting the given values, we get:1/-25 cm = 1/100 cm + 1/diSolving for di, we get:di = -20 cmThe negative sign indicates that the image is virtual and upright.The image height is then given by:hi = -di * ho/dowhere ho is the object height.Substituting the given values, we get:hi = -(-20 cm) * 4.0 cm/100 cm= 0.8 cmTherefore, the height of the image is 0.8 cm.

A Mirror with a Focal Length -25 Cm Has a 4.0