Density is defined as its mass divided by its volume. In the same way density of nucleus is defined as the ratio of mass of nucleus to its spherical volume. The mass of nucleus is equal to number of nucleons in nucleus (A) and the mass of single nucleon (m). Since mass of neutron and proton are same.

M = A m.

Nucleus is spherical in shape with radius r. So volume of nucleus (V) = 4/3(Π r³).
So Formula of density of a nucleus.

Where A = number of nucleons in nucleus

m = mass of single nucleon

r = Radius of nucleus.

Experiments that studies the size of nuclei indicate that the volume of nuclei is directly proportional to the total number of nucleons present.

V_n ∝ A  

where V_n = volume of nuclei and A = mass number

For sphere, V ∝ r³

where r = radius of a nucleus

Substituting value of V in above equation we get,

r³ ∝ A

So, r ∝ A^1/3

Using R₀ as a proportionality constant we get,

r = A^1/3 R₀

where A = mass number, r = radius of a nucleus and R₀ = proportionality constant.

R₀ = 1.25 fm (femtometre) with typical deviations of up to 0.2 fm from this value.

Atomic mass unit is taken to be the 1/12th of the actual mass of carbon isotope 6C12
The value of Atomic mass unit (a.m.u.) is given as,
1 a.m.u. = 1.66 × 10-27 kg
1 a.m.u. = 931 × 106 eV
1 a.m.u. = 931 MeV

Electron volt is defined as the energy acquired by an electron when it is accelerated through a potential difference of 1 volt.

The value of electron volt (eV) is given as,

1 eV = (1.602 × 10-19 coulomb) × (1 volt)
1 eV = 1.602 × 10-19 joule

The value of milli-electron volt (MeV) is given as,

1 MeV = 105 eV
1 MeV = 1.602 × 10-13 J

As per Bragg’s law, certain crystals at certain specific wavelengths and incident angles produced intense peaks of reflected radiation.

The formula for Bragg’s law is given as,
 n λ = 2d sinƟ

λ = wavelength                    
Ɵ = glancing angle
d = spacing between atomic planes
n = Integer series of reflection.