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Find the focal length of a concave mirror that produces four times larger real image of an object held at 5cm from the mirror.

User Seanf
by
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1 Answer

6 votes

Answer:

6.67 cm

Step-by-step explanation:

Given

  • h (image) = 4 x h (object)

Finding magnification

  • m = h (image) / h (object)
  • m = 4 x h (object) / h (object)
  • m = + 4.0

Finding image distance

  • m = - (image distance / object distance)
  • 4 = - (v / 5)
  • 4 = -v/5
  • v = -20
  • v = -20 cm

Mirror formula

  • 1/f = 1/v + 1/u

Solving

  • 1/f = 1/-20 + 1/5
  • 1/f = -1 + 4/20
  • 1/f = 3/20
  • f = 20/3 cm
  • f = 6.67 cm
User Ezequiel Tolnay
by
7.4k points