Assignment Key: How Radiation Affects Living Cells

  1. Using the definition of a sievert, as an absorbed dose of one joule per kilogram (J/kg), calculate the total amount of energy (in joules) absorbed by a 750 g guinea pig at the lethal dose level.
    3.00 J

  2. Using the definition of a sievert, calculate the total amount of energy (in joules) absorbed by a 2.34 kg rabbit at the lethal dose level.
    18.7 J

  3. Assuming the lethal dose for a human is 4.1 Sv, calculate the total amount of energy (in joules) absorbed by a 58 kg adult at the lethal dose level.
    238 J

  4. A typical cup of tea (250 mL) when consumed at 85oC will yield nearly 200 J of thermal energy to a human's stomach.
    a) What absorbed dose of radiation would be required to deliver the same amount of energy to a 60 kg human (by radiation)?
    3.33 Sv, which is in the lethal dose range for humans.
    b) What is the difference between these two cases (i.e. energy from a teacup and energy from incident radiation)?
    Scientists express this as a difference in the "energy density" of hot tea and absorbed radiation. In tea, the energy is "spread out" (high entropy1) and is more-or-less uniformly distributed throughout the liquid, whereas the energy delivered as radiation is extremely localized (low entropy1) and delivers exceptionally large amounts of energy into very tiny spaces.
    1Note: The term "entropy" is used to describe the relative state of orderliness or randomness of a system. Highly disordered and highly randomized systems are said to have "high entropy".

  5. The chart below shows the maximum permissible absorbed dose for occupational exposure. Complete the chart by calculating the total absorbed energy and the number of equivalent proton absorptions needed to produce this effect.
    body part absorbed dose
    (Sv ·a-1)    		 energy (J ·a-1·kg-1) number(n) of absorbed
    2GeV protons
    (n·a-1·kg-1)
    skin 0.15 1.5x10-1 ~ 4.68x108
    hands 0.75 7.5x10-1 ~ 2.34x107
    forearms 0.30 3.0x10-1 ~ 9.36x108
    bone marrow 0.05 5.0x10-2 ~ 1.56x106
    lenses of the eyes 0.04 4.0x10-2 ~ 1.25x106
    Sv·a-1 = sievert per year
    1J = 6.24x1018eV

ASSESSMENT

The chart that follows identifies four levels of achievement for assessing students' communication of information and ideas. Levels 1 and 2 describe performance that is approaching the standard for the grade; level 3 describes the standard for the grade; and level 4 describes performance that is above the standard. In numerical terms, all four levels are at passing level for the grade. Level 1 corresponds to a mark of 50%-59%; level 2, 60%-69%; level 3, 70%-79%; and level 4, 80%-100% . Student performance that is not approaching or is significantly below the standard would receive a failing grade.
Understanding of Basic Concepts

The student:
Level 1
Level 2
Level 3
Level 4
demonstrates limited understanding of how radiation affects living cells by solving problems related to absorbed radiation doses with limited accuracy demonstrates some understanding of how particle radiation interacts with matter by solving problems related to absorbed radiation doses with some accuracy demonstrates considerable understanding of how particle radiation interacts with matter by solving problems related to absorbed radiation doses with general accuracy demonstrates thorough understanding of how particle radiation interacts with matter by solving problems related to absorbed radiation doses with a high degree of accuracy
Inquiry

The student:
Level 1
Level 2
Level 3
Level 4
interprets and uses data relating to radiation exposure with limited competence making major errors/omissions interprets and uses data relating to radiation exposure with moderate competence making several minor errors/omissions interprets and uses data relating to radiation exposure with considerable competence making few minor errors/omissions interprets and uses data relating to radiation exposure with a high degree of competence making practically no errors/omissions
Communication of Information and Ideas

The student:
Level 1
Level 2
Level 3
Level 4
uses scientific terminology, symbols, conventions, and SI units with limited accuracy and effectiveness uses scientific terminology, symbols, conventions, and SI units with some accuracy and effectiveness uses scientific terminology, symbols, conventions, and SI units with considerable accuracy and effectiveness uses scientific terminology, symbols, conventions, and SI units with a high degree of accuracy and effectiveness

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Prepared by the YES I Can! Science Team,