Given the ratio of kinetic energy of an electron in two orbitals is $16:9$. Calculate the ratio of the wavelength of the electron waves.

The mass of an electron is $9.1 \times 10^{-31} \ kg$. If its $K.E.$ is $3.0 \times 10^{-25} \ J$,calculate its wavelength.

What is the mass of a particle with a wavelength of $3.313 \mathring{A}$ moving with a speed of $2.0 \times 10^8 \ m \ s^{-1}$?

The de-Broglie wavelength $(\lambda)$ for electron $(e)$, proton $(p)$ and $He^{2+}$ ion $(\alpha)$ are in the following order. (Speed of $e$, $p$ and $\alpha$ are the same)

State the de-Broglie principle and explain it.

For which of the following does the mathematical expression $\lambda = \frac{h}{p}$ stand?