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.

de-Broglie’s hypothesis states value of a wavelength associated with a particle of mass m which is moving with speed v.

The formula for de-Broglie’s hypothesis is given as,

Wavelength = Planck’s constant / momentum

λ = h / p…………………..(1)

We know that momentum = mass × velocity

substituting value of p in (1) we get,

 λ = h / mv

 λ = wavelength                                     h = Planck’s constant

p = momentum                                     m = mass

v = velocity

Half-life period is used in nuclear physics to describe how quickly unstable atoms undergo, or how long stable atoms survive a radioactive decay. It is the time required for a quantity to reduce to half its initial value.

we know N = N₀ e^-λt and half life T = t  , N = N₀ / 2

substituting these values we get,

N₀/ 2 = N₀ e^-λt

1/ 2 = e^-λt

e^λt = 2

λ T = log _e 2

λ T = 0.693 —– value of log _e 2 is 0.693

T = 0.693 /λ

Where

T = half-life period

λ =the decay constant of the decaying quantity.

The decay constant is defined as the ratio of amount of substance decayed per unit time to amount of substance present at that time.

we know ,

N = N₀ e^-λt

and t = 1 /λ

Substitute t= 1 /λ in above formula we get

N = N₀ e^-λ(1/λ)

N = N₀ e^-1

N = N₀ / e

N = N₀ /2.718

N = 0.37 N₀

Now decay constant can also be defined as the reciprocal of the duration in which a substance decays at 37% of its original quantity.