Who developed quantum mechanics?

Give the difference between $\psi$ and $|\psi|^2$.

If the uncertainty in velocity is $\frac{1}{2m} \sqrt{\frac{h}{\pi}}$, then the ratio of uncertainty in position and momentum is (in $: 1$)

$A$ dust particle has a mass of $10^{-11} \, g$,a diameter of $10^{-4} \, cm$,and a velocity of $10^{-4} \, cm \, sec^{-1}$. If the error in the measurement of velocity is $0.1 \%$,what is the uncertainty in its position?

The uncertainty in the position of a moving bullet of mass $10 \ g$ is $10^{-5} \ m$. Calculate the uncertainty in its velocity.

The position of both an electron and a helium atom is known within $1.0 \, nm$ and the momentum of the electron is known within $50 \times 10^{-26} \, kg \, m \, s^{-1}$. The minimum uncertainty in the measurement of the momentum of the helium atom is