Energy, matter and radiation (much more interesting than it looks like) (well not really, but shut up and take notes)

Let’s define each term!  Energy: measured in Joules (J), it corresponds to the ability of a system to do work on another one. It cannot be created or destroyed; the quantity of energy is constant, it can only be transferred from one system to another.  Matter: measured in kilograms (kg), it’s defined by anything that has mass and volume, or, in a more scientist definition, everything that is made up by atoms and molecules.  Radiation: radiations are a process in which energetic particles or energetic waves travel through vacuum or matter. There are two kinds of radiations: ionizing ones and non- ionizing ones.

A quick reminder on radiations

Where do radiations come from?  We’re constantly exposed to radiations!  There are a lot of different sources: o Cosmic radiation (radiations from the sun and stars) o Terrestrial radiation (soil, vegetation…) o Internal radiation (your own body!) o X-rays (medicine, airport security…)

How much radiation are we exposed to?

A few formulas (1)

A few formulas (2)

A few formulas (3)

 Inverse Square Law

What happens when radiation encounters a material? Radiations can whether be ionizing or non ionizing.

Non-ionizing radiations  Non-ionizing radiations: not enough energy to ionize atoms or molecules (visible light, infrared, microwave…) Two possibilities o Reflection o Transmission

Ionizing radiations  Ionizing radiations : enough energy to ionize atoms or molecules, and therefore deposit energy; absorbed by matter.  Alpha and beta particles : deposit energy through electrical interactions with electrons in the material.  Gamma rays and X rays : liberate atomic (orbiting) electrons, which then deposit energy in interactions with other electrons.  Neutron : deposit energy through collisions with nuclei that contain protons.  Protons : set in motion and, being charged, they again deposit energy through electrical interactions.

Abilities of ionizing radiations to penetrate solid matter

Let’s recap! Matter RadiationsEnergy Emits Carry Affects