A concave mirror forms a real image at 17.0 cm from the mirror surface along the principal axis. If the corresponding object is at a distance of 36.0 cm, what is the mirror's focal length?

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Answer 1 · 2016-12-16T16:02:03

The focal length is #=11.5 cm#

We use the " mirror formula"

#1/f=1/d_o +1/d_i#

Object distance #d_o=36cm#

Image distance #d_i=17 cm#

So,

#1/f=1/36+1/17=(17+36)/(17*36)=53/(17*36)#

#f=(17*36)/53=11.5cm#