Physics Final

What do PET scans need to be effective?

Radioactive tracer

What is radiation?

Emission or transmission of energy via waves or particles through space

Where does radiation come from?

Nucleus of an unstable atom

When does radioactive decay happen?

By changing the number of protons; an irreversible process

What is ionization?

The gain or loss of an electron

Define cation

Loss of an electron; positive charge

Define ion

Gain an electron; negative charge

What are the two types of radiation?

Ionizing and non-ionizing

Kinds of non-ionizing radiation:

• radio waves

• microwaves

• infrared

• visible light

• UV

Kinds of ionizing radiation:

• Alpha particles

• Beta particles

• Gamma rays

• X-rays

Characteristics of non-ionizing radiation:

• cannot remove electrons from atoms

• does not have sufficient energy to break molecular bonds

Characteristics of ionizing radiation:

• former energy that acts by removing electrons from atoms of materials

• can travel unseen, can pass through material

• can alter cells of our body

Natural sources of ionizing radiation:

• radiation from space

• radiation from earth

• radon

• building materials

Manmade sources of ionizing radiation

• x-rays

• CT or CAT

• PET

• Fluoroscopy

• nuclear medicine

Exposure unit

Roentgen (R)

SI Exposure unit

Coulombs per kilogram (C/kg)

Absorption unit

Rad (radiation absorbed does)

SI Absorption unit

Gray (Gy)

Dose equivalent

REM (Roentgen equivalent man)

SI Dose equivalent

Sievert (1 Sievert = 100 REMs)

Absorbed dose formula:

Absorbed dose= Energy absorbed/mass of absorbing material

Formula for Biologically Equivalent Dose (with units)

BED (REMs) = Absorbed does (RADs) x RBE (Relative Biological Effectiveness)

When is the nucleus stable?

When proton number equals neutron number (will stay stable indefinitely until an outside force interacts with it)

Why are atoms radioactive?

atom attempting to reach stability by objecting energy

Most to least penetrating ionizing radiation:

• gamma rays

• beta rays

• alpha rays

Alpha Decay

4/2 He

Beta Decay

0/-1 e

What is half-life?

the time it takes for half of the original volume to decay

Unit for radiation emission/source

Becquerel (SI); Curie (USA)

What happens during Alpha Decay

mass number decreases by 4 and proton number decreases by 2

What happens during beta decay

atom gains a proton, no change in mass

What can Carbon-14 be used for?

To determine the age of artifacts by comparing the amount of carbon-14 in the artifact to the amount in the living organism

What stage of matter is sound the fastest in?

Solid

Formula for speed of sound

vsound = 331m/s + (0.6m/sc)Temp

Speed of light

3.0 ×10^8m/s

Speed of sound

345m/s

formula for distance

distance = velocity x time

frequency determines…

pitch

amplitude determines…

loudness

waveform determines…

tone quality

Electricity is…

the flow of electrons around the circuit

An electric circuit consists of:

Energy source, energy consuming device, and wire

The measure of potential energy

Voltage (V)

formula for current (with units)

I (current/ ampere A) = q (charge/ Coulomb)/ t (time/ second)

What is the current of an x-ray tube measured in?

milliamperes (mA) -typically ranges .1 to 1A (100mA to 1000mA)

Direct Current (DC) -

changes move in same direction all times

Alternating Current (AC) -

charges flow reverse direction periodically

Resistance (R) -

ability of a material to slow or stop the flow of electric current (can adjust the amount of current; measure of opposition to current flow)

formula for Ohm’s Law (with units)

V (potential difference/ voltage)/ I (current/ A) = R (resistance/ Ohm’s)

Parallel circuits:

• current is shared while each one has same voltage

• failure doesn't affect all

• branches

• 1/R

Series

• multiple devices same circuit

• failure affect all

• no branches

• R

When unequal resistors are connect in series across an ideal battery…

the current flowing in each is the same