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Radioactivity Flashcards

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1
Q

mass of electron

A

9.1* 10^-31 kg

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2
Q

mass of proton

A

1.67*10^-27 kg (mass of neutron too)

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3
Q

in a nuclear reaction, what happens to A and Z

A

total sum of A/Z on product side= total sum of A/Z on reactants side

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4
Q

define isotopes

A

atoms of the same element, having same atomic number but different mass number

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5
Q

which element has most isotopes

A

tin

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6
Q

types of isotopes

A
  1. stable (n=p nearly)
  2. unstable/radioactive (n > p): undergo radioactive decay
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7
Q

define isobars

A

atoms of different elements which have the same mass number A, but different atomic number Z

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8
Q

define mirror isobars

A

if number of protons and neutrons get interchanged inside nucleus (Na and Mg)

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9
Q

define isotones

A

atoms having different number of protons but same number of neutrons, and different number of electrons

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10
Q

three types of becquerel rays

A
  1. positive (alpha)
  2. negative (beta)
  3. uncharged (gamma)
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11
Q

define radioactive substances

A

disintegrate by the spontaneous emissions of radiations (uranium, radium, polonium, thorium, actinium)

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12
Q

effect of physical and chemical changes on nature of radiation emitted by a substance and its rate of decay

A

no change

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13
Q

define radioactivity

A

it is a nuclear phenomenon. it is the process of spontaneous emission of alpha or beta and gamma radiations from the nucleus if atoms during their decay

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14
Q

properties of alpha particles

A
  1. consists of two protons and two neutrons- same as a doubly ionised helium atom
  2. mass is roughly four times the mass of proton, and charge is twice of proton
  3. speed is of the order 10^7 m/s
  4. strongly ionises the gas through which it passes (strongest ionising power than other two)
  5. dissipates its energy as it moves through a medium and therefore its penetrating power is quite small (least power)
  6. positive, so they are deflected by electric and magnetic fields
  7. affect photographic plate
  8. cause fluorescence on striking a fluorescent material
  9. large KE and momentum
  10. destroy living cells and cause biological damage
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15
Q

mass of alpha particle

A

6.68 * 10^-27 kg

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16
Q

specific charge of alpha particle

A

4.79 * 10^7 C/kg

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17
Q

mass of beta particle and charge

A

mass: 9.110^-31 kg
charge: -1.610^-19 C

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18
Q

specific charge of beta particle

A

1.76*10^11 C/kg

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19
Q

properties of beta particles

A
  1. fast moving electrons emitted from nucleus
  2. beta particles given out from nucleus of atom, and cathode rays are given out from its orbital electrons
  3. speed is 10^8 m/s
  4. ionise the gas through which they pass
  5. more penetrating power than alpha, less than gamma
  6. negatively charged so they get deflected by electric and magnetic fields (more deflection than alpha because it is lighter)
  7. affect photographic plate
  8. cause fluorescence on striking a fluorescent material
  9. produce xrays when stopped by metals of high Z and high mp
  10. cause more biological damage than alpha rays
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20
Q

properties of gamma radiations

A
  1. electromagnetic waves like x rays and light but differ in wavelength
  2. speed is same as speed of light in air
  3. lowest ionising power
  4. highest penetrating power (only thick sheet of lead can stop)
  5. not deflected by electric and magnetic fields as they are uncharged
  6. affect photographic plate
  7. cause fluorescence
  8. diffracted by crystals like x rays
  9. x rays obtained when there is a transition of electron in inner orbits, and gamma rays are produced when given out from nucleus
  10. biological damage
  11. cancer treatment
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21
Q

wavelength of gamma radiationm

A

10^-4 nm

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22
Q

most energetic radiations

A

gamma (so they have smaller rate of collisions with atoms of medium through which they pass; least ionising power; max penetrating power

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23
Q
A
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24
Q

change during emission of alpha and beta rays

A

change in number of protons and neutrons inside nucleus

25
Q

change during emission of gamma rays

A

change in energy of nucleus, not change in number of protons or neutrons

26
Q

alpha emission

A
  1. if an unstable nucleus containing more neutrons than the number of protons, may emit a particle containing two protons and two neutrons tightly bound together known as alpha particle
  2. if nucleus of radioactive element of A and Z emits an alpha particle, daughter nucleus will have mass number (A-4) and atomic number (Z-2)
27
Q

beta emission

A
  1. neutron changes to proton by emitting an electron for charge conservation
  2. number of NUCLEONS remains same, neutrons decrease by 1, protons increase by 1
  3. daughter product is isobar
28
Q

gamma emission

A
  1. occurs when daughter or parent nucleus is in a state of excitation
  2. takes no charge and no mass from nucleus
  3. no change in A and Z
29
Q

daughter product after alpha or beta emission

A

may be radioactive and may again decay, emitting more alpha or beta rays until nucleus is stable

30
Q

uses of radio isotopes

A
  1. medical
  2. scientific
  3. industrial fields
31
Q

medical use of radio isotopes

A
  1. treating leukemia, cancer
  2. salts of weak radio isotopes used for diagnosis (called tracers)
  3. radio cardiology
  4. gamma rays emitted by them used to sterilize bandages, dressings, syringes, other equipments
32
Q

scientific uses of radio isotopes

A
  1. alpha particles emitted used as projectiles for nuclear reactions, helps in estimating size of nucleus
  2. study the growth of plants by using chemical manure
  3. age of excavated material of archaeological importance, rocks- calculated by rate of decay of carbon 14 by beta emissions in dead plants (aka carbon dating)
33
Q

industrial uses of radio isotopes

A
  1. fuel for atomic energy reactors
  2. used by engineers in factories to avoid accumulation of charge on moving parts of machines due to friction
  3. luminiscent sighs due to ionising effect of radiations
  4. control thickness of paper, plastic and metal sheets during their manufacture
34
Q

sources of harmful radiations

A
  1. radioactive fallout from nuclear power plants
  2. nuclear waste
  3. cosmic radiation and x rays
35
Q

types of harmful biological effects of nuclear radiations

A
  1. short term recoverable effects- diarrhea, sore throat, loss of hair, nausea
  2. long term irrecoverable effects- leukemia, cancer
  3. genetic effects
36
Q

safety measures while establishing nuclear power plants

A
  1. ensure workers are not exposed to nuclear radiations and in case of any accident, there is a minimum spread of radiations
  2. nuclear reactor must be shielded with lead and steel walls
  3. reactor must be housed in airtight building of strong concrete structure that can withstand earthquakes
  4. must be back-up cooling system for reactor core, so the core is saved from heating and melting
37
Q

safety measures while handling radioactive materials

A
  1. put on special lead lined aprons and lead gloves
  2. handle the radioactive materials with long lead tongs
  3. special film badges used which are tested from timee to time to know the amount of radiations to which a particular person has been exposed
  4. radioactive substance must be kept in a thick lead container with narrow opening
38
Q

safety measures in safe disposal of nuclear waste

A

must be first kept in thick casks, then must be buried in specially constructed deep underground stores,
stores must be made far from populated areas

39
Q

background radiations

A

radioactive radiations to which we are all exposed, even in the absence of a visible radioactive source

40
Q

two types of sources of background radiations

A
  1. internal source (K-40, C-14, radium inside body)
  2. external source (cosmic rays, naturally ocurring radioactive elements like radon-222 and solar)
41
Q

1 MeV=

A

1.6 * 10^-13 J

42
Q

1 amu= ? MeV

A

931 MeV

1 amu of mass is equivalent to 931 MeV of energy

43
Q

define nuclear fission

A

process in which a heavy nucleus splits into two lighter nuclei of nearly the same size, when bombarded with slow neutrons

44
Q

why is energy released during fission

A

sum of masses of product nuclei is less than sum of mass of parent nucleus and mass of neutron

45
Q

what happens when a neutron strikes a uranium nucleus (A= 235)

A

unstable for of uranium (A= 236) formed, which splits into Barium (144, 56) and Krypton (89, 36). 3 neutrons are released and energy

46
Q

how much energy is released due to fission of one uranium nucleus

A

190 MeV

47
Q

why is U-235 more fissionable than U-238

A

fission of U-238 nucleus is possible only by the fast neutrons, while fission of U-235 nucleus can occur even by slow neutrons

48
Q

how is chain reaction controlled

A

by absorbing some of the neutrons emitted in the fission process by means of cadmium rods and then making them slow by the moderators (graphite, heavy water). the rate of energy generated in fission can be controlled and utilised for constructive purposes

49
Q

uses of fission

A
  1. destructive use
  2. constructive use
50
Q

for destructive use

A

nuclear bomb

51
Q

for constructive use

A

nuclear reactor to generate electric power

52
Q

define nuclear fusion

A

process in which two light nuclei combine to form a heavy nucleusr

53
Q

reason for release of energy during fusion

A

mass of the product nucleus is less than the sum of masses of two combining nuclei

54
Q

how much energy is totally released when 3 deuterium nuclei fuse to form helium nucleus

A

21.6 MeV
part of the energy is obtained as KE of neutron and proton

54
Q

why is fusion not possible at ordinary temperature and pressure

A

when two nuclei approach each other, due to their positive charge, the electrostatic force of repulsion between them becomes so strong that they do not fuse. high temp and pressure is required. both nuclei due to thermal agitations, acquire enough KE to overcome repulsion and fuse

55
Q

source of energy of sun

A

nuclear fusion of light nuclei present at the core at very high temp and pressure

56
Q

hydrogen bomb working

A

based on nuclear fusion, at high temp, required for fusion is produced by explosion of nuclear fission bomb

57
Q

why is energy released by fusion greater than fission for a given mass of heavy nucleus?

A

for the same mass, the number of light nucleus is much more than the number of heavy nucleus; hence, energy produced per unit mass in fusion is much larger than the energy obtained per unit mass in fission

58
Q

why can’t energy be produced by fusion in nuclear reactors

A

at high temperatures like 10^7 K, substance gets ionised, it is in plasma form. it is difficult to store plasma
this can be overcome by storing plasma in nano carbon tubes

Physics (12 decks)

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