Question

Prove that a convex lens can only form a virtual, erect and diminished image.

Answer 1

m = `"v"/"u"`

`1/"f" = 1/"v" - 1/"u"`

x^ly by u

`"u"/"f" = "u"/"v" - 1`

`"u"/"f" + 1 = 1/"m"`

`("u + f")/"f" = 1/"m"`

m = `"f"/("u + f")`

m > 0  → (virtual)

m = `"f"/("u + f")`

O < m < 1  → diminished

m = `"I"/"O"` > 0

I → Erect