Question

When using a shaving mirror with a focal length of 72 cm to view the image the face, if the face is 18 cm from the mirror, determine the image distance and the magnification of the face.

Answer 1

Using the two relationships on mirrors: -

1/do+1/di =1/f

where  

d  is the distances of object and image from the mirror and  

f  is the mirror`s focal length

The magnification  

m =  −  di/do

Thus, 1/18+1/di = 1/72

di = -24cm negative and virtual

m = -(-24/ 18)  = 1.33

Thus, 1.33 times the object and positive (upright).

Answer 2

Answer:

Using the two relationships on mirrors: -

1/do+1/di =1/f

where  

d  is the distances of object and image from the mirror and  

f  is the mirror`s focal length

The magnification  

m =  −  di/do

Thus, 1/18+1/di = 1/72

di = -24cm negative and virtual

m = -(-24/ 18)  = 1.33

Thus, 1.33 times the object and positive (upright).