convex lens object at the focal point

[nhernandez4]

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For convex lens when object at focal point will their be image. Just took a gold standard test and it explained that there is no image. But, I was doing a exam c. passage and said if object at focal point there will be image( at infinity)???????????????????

 

[MCATBear]

If you take the thin lens equation 1/f = 1/di + 1/do, when 1/do = 1/f (object at focal point) then 1/di must = 0 (so 1/inf) so mathematically the image is at infinity. Practically speaking, I think that means there is no image you can see, so both answers are kind of correct.