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Answered

at what position an object be placed in front of a concave mirror of radius of curvature 40cm so that an erect image of magnification of 3 be produced ?

Answer :

  • C=40cm
  • f=C/2=40/2=20

  • m=3

[tex]\\ \sf\longmapsto m=\dfrac{f}{f-u}[/tex]

[tex]\\ \sf\longmapsto 3=\dfrac{20}{20-u}[/tex]

[tex]\\ \sf\longmapsto 3(20-u)=20[/tex]

[tex]\\ \sf\longmapsto 60-3u=20[/tex]

[tex]\\ \sf\longmapsto 3u=40[/tex]

[tex]\\ \sf\longmapsto u=13.3cm[/tex]

  • m=magnification
  • f is focal length
  • C is radius of curvature
  • u is object distance

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