Physics and Radiography Key Concepts

matter

Anything with mass that takes up space.

mass

Amount of matter.

weight

Force from gravity.

energy

The ability to do work; measured in Joules (J) or kV for X-rays.

radiation

Energy emitted and transmitted through matter.

atom

Smallest part of an element.

radiography

Both an art and a science.

scientific method

Collect facts → study relationships → draw conclusions.

physical science

Study of non-living matter (ex: physics).

biological science

Study of living matter (ex: anatomy & physiology).

molecule

Smallest part of a compound.

mixture

Two or more substances combined.

states of matter

Solid, liquid, gas.

E=mc²

Matter and energy can change forms but cannot be destroyed.

periodic table

Created by Mendeleev.

Bohr's model

Proposed electrons orbit the nucleus like a mini solar system.

quantum physics principles

Developed by Schrodinger.

nucleus particles

Protons (+) and neutrons (0).

electrons

Have a negative (-) charge.

string theory

Electrons and quarks may be vibrating strings, not particles.

alpha particles

2 protons + 2 neutrons; stopped by paper or skin.

beta particles

Electrons (-) or positrons (+); penetrate farther than alpha.

gamma rays

High-energy photons; no mass/charge; penetrate deeply.

half-life

Time for half of radioactive atoms to decay.

isotopes

Same protons, different neutrons.

ionization

Atom gains or loses electrons → becomes an ion.

electron shell capacity

2n² (n = shell number).

octet rule

Outer shell ≤ 8 electrons → full = stable.

Z# (atomic number)

Number of protons → identifies the element.

valence +1

Gives one electron to become stable.

valence -1

Gains one electron to become stable.

ionic bond

Transfer of electrons.

covalent bond

Sharing of electrons.

mechanical energy

Potential = at rest, kinetic = motion.

chemical energy

Energy from chemical reactions.

thermal/heat energy

Energy from molecular movement; measured by temperature.

electrical energy

Energy from moving electrons in a conductor.

nuclear energy

Energy from breaking bonds in the nucleus.

electromagnetic energy

Energy from electric + magnetic fields; >10 eV = ionizing.

X-rays discovery

Wilhelm Rontgen, 1895.

X-rays behavior

Travel in straight lines, penetrate matter, can ionize, affect film, produce scatter.

Can X-rays be focused by a lens?

No.

energy from X-rays interacting with matter

Secondary radiation, scatter radiation, heat energy.

current

Flow of electrons (-→+).

resistance

Opposition to current; ↑length ↑resistance, ↑diameter ↓resistance, ↑temp ↑resistance.

Ohm's Law formula

V = I × R

Power formula

P = I × V

series circuit effect

One component out → all out.

parallel circuit effect

One component out → others stay on.

protective devices

Circuit breakers, fuses, grounding.

EM radiation

Energy from combined electric and magnetic fields traveling through space.

speed of EM radiation

The speed of light = 3 × 10⁸ m/s.

ionizing EM energies

Energies above 10 eV (ex: X-rays, gamma rays, UV).

order of EM spectrum

Radio → Microwave → Infrared → Visible → UV → X-ray → Gamma.

wave equation

Velocity = Frequency × Wavelength (v = f × λ).

wavelength and frequency relationship

Inverse; as wavelength ↑, frequency ↓.

wavelength and energy relationship

Inverse; longer wavelength = lower energy.

frequency and energy relationship

Direct; higher frequency = higher energy.

photon

A small packet of EM energy with no mass or charge.

Planck's constant (h)

Relationship between photon energy and frequency.

value of Planck's constant

h = 4.15 × 10⁻¹⁵ eV·sec.

formula for photon energy

E = h × f.

photon energy and frequency relationship

If frequency doubles, energy doubles.

speed of light

3 × 10⁸ m/s.

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