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particles Flashcards

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Physics 101 flashcards AP® Physics flashcards
1
Q

give an example of mechanical waves

A

water waves
waves of a rope

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2
Q

transverse waves

A

particles vibrate perpendicular to the direction of the eave

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3
Q

longitudinal waves

A

particles vibrate in the same direction as the direction of motion

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4
Q

longitudinal waves example

A

sound waves

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5
Q

properties of waves

A

reflection
refraction
interference

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6
Q

what size wavelength gives red light

A

630 to 700 nm

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7
Q

what size wavelength gives blue light

A

440 to 480 nm

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8
Q

electromagnetic spectrum from shortest to longest wavelength

A

gamma
x rays
ultra violet
visible
infrared
microwaves
radio waves

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9
Q

how do waves transmit energy

A

oscillations

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10
Q

Wiens law

A

λpeak x T = 2.9x10^-3 mK

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11
Q

radiation as a diagnostic tool - IR

A

penetrates only the outer layers of tissue and is used to investigate injuries, stresses, skin burns close to the surface

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12
Q

radiation as a diagnostic tool - ultrasound

A

5 MHz scanned over the body and echos from internal organs are used to make an image

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13
Q

radiation as a diagnostic tool - Xrays

A

goes right through tissue and is used to check broken bones

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14
Q

radiation as a diagnostic tool - gamma rays

A

destroys cancer cells and can also be used as an imaging method using a tracer

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15
Q

photoelectric effect

A

the emission of electrons from a metal when light of sufficient energy is shone on it

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16
Q

explain the properties and organisation of electrons, protons and neutrons

A

electrons
- negative charge
- in electron cloud
- mass of 9.11 x10^-31

protons
- positive charge
- in nucleus
- mass of 1.672 x 10^-27

neutrons
- no charge
- in nucleus
- mass of 1.676 x 10^-27

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17
Q

How does Computerized Axial Tomography (CAT) work? Explain your answer
with the aid of a diagram.

A
  1. thin beam of x-rays pass through the region of interest
  2. detectors measure the amount of x-rays that passes through the sample
  3. the x-ray beam and detector are rotated around the sample in very small steps
  4. a computer builds all this information into an image
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18
Q

Explain how a CAT scan differs from a regular X-ray in
terms of the method and usefulness of the resulting image.

A
  • in an x-ray a single beam of x-rays is passed through the body
  • in a CAT scan multiple x-ray beams are emitted from different angles
  • convential x-rays provide limited information as the images are superimposed with shadows and there is no dept
  • with CAT you can view the images in multiple planes and in more detail
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19
Q

alpha radiation

A
  • consists of particles composed of 2 neutrons and 2 protons
  • reduces the atomic number of the parent nucleus by 2 and the mass number by 4
  • poor penetrating power; stopped by paper
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20
Q

beta radiation

A
  • consists of high energy electrons
  • (a neutron turns into a proton and an electron is emitted)
  • negative charge
  • stopped by few mm of aluminium
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21
Q

gamma radiation

A
  • high energy electromagnetic waves
  • no charge
  • high penetration, stopped by a few cm of lead
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22
Q

Describe a diagnostic imaging method which relies on beta+ and electron-positron
annihilation. Specifically name:
- the method
- describe how it works
- why it is useful in the medical field with the aid of an appropriate diagram

A
  • beta+ is the basis of PET
  • the patient drinks/is injected with a position emitting nuclide.
  • when this positron meets an electron, two gamma rays are emitted and head in opposite directions
  • the uptake of biological components in tissue is mapped by measuring the gamma rays recorded in different directions
  • gives an accurate diagnosis, can give early detection which allows for early treatment
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23
Q

what is the mass defect of a nucleus and why is it important to the structure of matter

A

difference between the mass of an atomic nucleus and the sum of the masses of its protons and neutrons

mass defect represents the binding energy (amount of energy required to break nucleus into its individual protons and neutrons)

nuclear stability: nuclei with lower mass defects are more stable

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24
Q

Quantum theory relation to photoelectric effect

A

the photon releases an electron only if the energy of the photon is greater than or equal to the work function of the metal

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25
Q

Uncertaincy Principle

A

we cannot measure the position and momentum of a particle at the same time

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26
Q

Milkman’s Expirement

A

put a charge on a tiny drop of oil
measured how strong an electric field has to be in order to stop the oil drop from fallinf

27
Q

medical uses of LASERs

A
  • therapeutic
  • narrow intense beam can be used to treat detached retina
  • welding broken tissue
  • removal of plaque clogging arteries
  • reduce bleeding
  • treat tumours
  • eye surgery
28
Q

how are x-rays produced

A

when rapidly moving electrons that have been accelerated through a large potential difference strike a metal target

29
Q

dielectrics

A

most capacitors have dielectrics
- a non conduction material between the two plates
- they physically maintain the separation
- decrease voltage
- increase capacitance (if no charge)

30
Q

electrostatics vs electric current

A

electrostatics: charges at rest
electric current: charges in motion

31
Q

loop rule

A

the sum of the potential charges around any closed circuit = 0

32
Q

junction rule

A

the current entering a point in a circuit = current leaving that point

33
Q

resistors in series

A

R = R1 + R2 + R3

34
Q

Resistance in parallel

A

1/R = 1/R1 + 1/R2

35
Q

resistance equation that includes resistivity

A

R = (resistivity x length) / Area

36
Q

perfect conductor

A

resistivity = zero

37
Q

perfect resistor

A

resistivity = infinity

38
Q

power in a circuit

A

P = iR

39
Q

capacitors in parrallel

A

C = C1 + C2

40
Q

capacitors in series

A

1/C = 1/C1 + 1/C2

41
Q

in a circuit with a capacitor current only flows when …

A

the capacitor is charging or discharging

42
Q

RC circuits in medicine

A

ventricular fibrillation - rapid uncoordinated contractions, no blood is pumped

fibrillation can often be stopped using a capacitor charged to about 1000V and discharged directly through the chest cavity

43
Q

pacemaker

A

an application of the RC circuit

in normal circumstances a pacemaker regulates heart beat, failure of this natural mechanism can be rectified using an artificial0 heart pacemaker

44
Q

what is a semi conductor

A

a type of material that falls between insulators and conductors on ability to conduct electricity

45
Q

what is p-type doping and n-type doping

A

p-type doping
is when the semiconductor is doped with s material that introduces more positive charge.

n-type doping
is when the semi conductor is doped with a material that introduces extra negative charge (electrons)

46
Q

conductors

A

materials where the charge can flow freely and conduct electricity, eg. metalsn

47
Q

insulators

A

materials that have almost no “free electrons”. they do not generally conduct electricity.

48
Q

right hand grip rule

A
  • point your thumb in direction of motion of the electric current
  • curl your fingers around
  • fingers point in the direction of magnetic field
49
Q

flemings left hand rule

A
  • thumb points in direction of force
  • pointer finger in direction of magnetic field
  • middle finger in direction of current
50
Q

formula for blood speed across an artery

A

velocity = V / (d x B)

51
Q

mass spectrometer

A
  • can measure the masses and relative concentrations of atoms and molecules
  • particles are ionized
  • ions are accelerated through a magnetic field
  • ions pass through a magnetic or electric field that causes them to deflect based on their mass to charge ratio.
    (light ions more in smaller circles and hit the detector closer to the entry point)
  • ions are detected based on their deflections
52
Q

velocity selector

A

it is used with a mass spectrometer to select ions with the same velocity for analysis

53
Q

application of a mass spectrometer

A
  • analysis of proteins and polypeptides in biological samples
  • used to analyze blood and urine
54
Q

formula for force on a length of wire

A

F = BiL

55
Q

if the voltage in a circuit is 220V and the power is 0.5kW, what is the resistance in the circuit

what equation would you use

A

P = V^2 / R

56
Q

formula for electric field (E)

A

electric field (E) = F/q

57
Q

why is PET useful in a medical field

A
  • can detect changes in cellular function and metabolism, allowing for the early detection and diagnosis of various diseases
  • PET scans can be used to monitor how well a patient is responding to treatment over time
58
Q

what does photo electric effect tell us about electronic orbits in atoms

A

When light of sufficient energy (photons) strikes a metal surface, it can cause the ejection of electrons from the metal. However, electrons are only emitted if the energy of the incident photons exceeds a certain threshold, called the work function. This observation suggests that electrons in atoms are restricted to specific energy levels, and only photons with energies corresponding to these levels can interact with the electrons.

59
Q

what is the significance about the number of electric field lines

A

the closer the field lines are together the stronger the electric field

60
Q

explain fusion and fission

A

fusion - when two lighter nuclei come together to form a heavier nucleus, releasing energy. high temp needed for fusion

fission - splitting of an unstable nucleus into two smaller ones with the release of energy

61
Q

if the currents flow in the opposite direction is the force attractive or repulsive

A

repulsive

62
Q

what is the binding energy of a nucleus

A

(amount of energy required to break nucleus into its individual protons and neutrons)

63
Q

electric current

A

rate at which electric charge flows through a given point in an electrical circuit

Physics (3 decks)

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