Question

Can the focal length of a lens is zero? if yes /no why?

Answer 1

Answer:

no it can't be zero . it's not physically possible.

Answer 2

In physically focal length of lens can't be zero because it always tends to be 0.

As

power = 1/focal length

so

if focal length = 0

then

power = 1/0 = infinity

which cannot be possible for a lens that a light from came from infinite distance with indistinguable with a parallel to principal axis .

So

focal length must be tends to 0 .