When an object is placed in front of a convex lens at its principal focus, image is formed at infinity. I wonder how to calculate how large this image will be. I mean what is the magnification in this case?

  • $\begingroup$ Use angular magnification and compare the visual angle formed at infinity with the visual angle of the image when it is formed at the near point of the eye. $\endgroup$ – Farcher Feb 15 '17 at 9:41
  • $\begingroup$ @Farcher Focal length of a convex lens is 5cm. What is the angular magnification when the final image is formed at infinity? $\endgroup$ – rock Feb 15 '17 at 10:13
  • $\begingroup$ I am not here to do your homework. I have given you all the information you need. hyperphysics.phy-astr.gsu.edu/hbase/geoopt/simmag.html $\endgroup$ – Farcher Feb 15 '17 at 12:39

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