Question

State whether the following statements are True(T) or False(F).

$S_1$ : Bohr model is applicable for $B{e}^{2+}$ ion.
$S_2$ : Total energy coming out of any light source is integral multiple of energy of one photon.
$S_3$ : Number of waves present in unit length is wave number.
$S_4$ : e/m ratio in cathode ray experiment is independent of the nature of the gas.

• A. FFTT
• B. TTFF
• C. FTTT
• D. TFFF

Answer 1

Answer: (C)

FTTT

${}_4^{8}Be$ atom has four electrons in outer shells,and four protons and four neutrons in its nucleus, After loosing two electrons it becomes, $B{e}^{++}$, which still has two electrons. Bohr model holds good for single electron atoms not for multiple electron systems. "$S_1$ is false."
Since electrons can stay only in stable orbits for which $mvr=\frac{nh}{2\pi }$, therefore in optical transition only specific energy quantum are possible. "$S_2$ is true. "
Wave number $k=\frac{2\pi }{\lambda }$. "$S_3$ is true. "
$e/m$ ratio is universal quantity known as the specific charge of electrons does not depend on the nature of atom where this electron belongs to. "$S_4$ is true. "