is it possible to open a pen cap with one finger? Why?

Why is it not possible to see an atom with naked eyes?

Is it possible for a given lens to act as a converging lens in one medium and a diverging lens in another medium?

12 defective pens are accidentally mixed with 132 good ones.It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen taken out is a good one.

Why preparation of aryl halide is not possible by reaction of phenol with PCl_3 ?

Why is it possible to write on rough blackboard with chalk ?

Is it possible to have length and velocity both as fundamental quantities? Why?

Is it possible to place a satellite, so that it is always over New Delhi? Why?

Why it is not possible to measure the voltage of an isolated reduction half reaction or the potential of a single electrode?