light - physics

• bonkysleuth

  12 Nov 08, 21:43

  An object 3cm high is placed 12cm from a converging lens. A real image is found to form 36cm from the lens.

   

  (a)what is the height of the image?

  (b) what is the focal length of the lens?

   

  Please help me out with part(a). for part (b), do you use 1/12 + 1/36?

   

  thanks.

• skythewood

  12 Nov 08, 21:58

  b)

  1/v = -1/u + 1/f

  u = object, v = image, f = focal length

  so you got it.