An object is placed in front of a concave mirror of focal length 30 cm. The virtual image of the object is obtained at a distance 20 cm from the mirror. Calculate the position of the object.

 

Please explain briefly step by step

Asked by chpratik11 | 28th Jun, 2019, 09:22: PM

Expert Answer:

Focal length f=-30cm
Image distance v=20cm
object distance u=?
 
According to mirror formula
1 over v plus 1 over u equals 1 over f
fraction numerator begin display style 1 end style over denominator begin display style 20 end style end fraction plus fraction numerator begin display style 1 end style over denominator begin display style u end style end fraction equals fraction numerator begin display style 1 end style over denominator begin display style negative 30 end style end fraction
fraction numerator begin display style 1 end style over denominator begin display style u end style end fraction equals negative fraction numerator begin display style 1 end style over denominator begin display style 20 end style end fraction minus fraction numerator begin display style 1 end style over denominator begin display style 30 end style end fraction
fraction numerator begin display style 1 end style over denominator begin display style u end style end fraction equals fraction numerator begin display style negative 3 minus 2 end style over denominator begin display style 60 end style end fraction
fraction numerator begin display style 1 end style over denominator begin display style u end style end fraction equals fraction numerator begin display style negative 5 end style over denominator begin display style 60 end style end fraction
u equals negative 12 c m
the object is placed at a distance of 12cm from the mirror.

Answered by Utkarsh Lokhande | 29th Jun, 2019, 07:51: AM