Answer:
Option B
Planetary
Explanation:
In 1913, Niels Bohr proposed a model to explain the stability of orbits around the nucleus. Niels believed that light is emitted by an electron when the electron's energy changes. Bohr Atomic Model is sometimes called planetary model because it resembles a mini-solar system.
Answer:
Option B

Explanation:








Centripetal acceleration 
Tangential component=dr=2*1.75=3.5

It has to do with mechanical engineering
(a) The number of vacancies per cubic centimeter is 1.157 X 10²⁰
(b) ρ = n X (AM) / v X Nₐ
<u>Explanation:</u>
<u />
Given-
Lattice parameter of Li = 3.5089 X 10⁻⁸ cm
1 vacancy per 200 unit cells
Vacancy per cell = 1/200
(a)
Number of vacancies per cubic cm = ?
Vacancies/cm³ = vacancy per cell / (lattice parameter)³
Vacancies/cm³ = 1 / 200 X (3.5089 X 10⁻⁸cm)³
Vacancies/cm³ = 1.157 X 10²⁰
Therefore, the number of vacancies per cubic centimeter is 1.157 X 10²⁰
(b)
Density is represented by ρ
ρ = n X (AM) / v X Nₐ
where,
Nₐ = Avogadro number
AM = atomic mass
n = number of atoms
v = volume of unit cell
A. Physical I/O sensors
Safety switches, operator inputs, travel limit switches etc