Understanding α, β, and γ Radiation: Inverse Square Law and Logarithms in Nuclear Physics

More about α, β and γ Radiation Nuclear Physics Lesson 3

Homework • Find out how they determined the nature of α, β and γ radiation.

Learning Objectives Recall what is meant by the term ionisation. Derive the inverse square law. Recall the equations for radioactive change.

Inverse Square Law The intensity, I, of the radiation is the radiation energy per second passing normally per unit area. (so intensity = energy per second/area) If a point source emits n photons per second, then the energy per second from the source is =nhf. The area radiated into is a sphere of radius r, where r is the distance from the source = 4πr2

Inverse Square Law So the intensity, I of the radiation at this distance: This equation is often written in the form:- where k is a constant

Logarithms 100 = 102 In this statement we say that 10 is the base and 2 is the power or index. Logarithms provide an alternative way of writing a statement such as this. We rewrite it as log10 100 = 2 This is read as ‘log to the base 10 of 100 is 2’.

Logarithms

Logarithms I like to think of logba as meaning “what power of b is a?” So log1010000 translates to:- “what power of 10 is 10,000?”  =4 So log327 translates to:- “what power of 3 is 27?”  =3

Another Example 25 = 32 we can write this as log2 32= 5 Here the base is 2 and the power is 5. We read this as ‘log to the base 2 of 32 is 5’.

Understanding α, β, and γ Radiation: Inverse Square Law and Logarithms in Nuclear Physics