The work functions of two metals ($M_A$ and $M_B$) are in the $1:2$ ratio. When these metals are exposed to photons of energy $6 \ eV$, the kinetic energy of liberated electrons of $M_A:M_B$ is in the ratio of $2.642:1$. The work functions (in $eV$) of $M_A$ and $M_B$ are respectively.

If the velocity of the revolving electron of $He^{+}$ in the first orbit $(n=1)$ is $v$,what is the velocity of the electron in the second orbit $(n=2)$?

Given below are two statements.
Statement $I:$ According to Bohr's model of an atom,qualitatively the magnitude of velocity of electron increases with decrease in positive charges on the nucleus as there is no strong hold on the electron by the nucleus.
Statement $II:$ According to Bohr's model of an atom,qualitatively the magnitude of velocity of electron increases with decrease in principal quantum number.
In the light of the above statements,choose the most appropriate answer from the options given below:

Vibrational energy is

The energy associated with the electron in the first orbit of a hydrogen atom is $-2.18 \times 10^{-18} \ J$. The frequency of the light required (in $Hz$) to excite the electron to the fifth orbit is $(h = 6.6 \times 10^{-34} \ Js)$

What is the packet of energy called?