The exponential law

Question 1

Define exponential relationship

Answer 1

• Mathematical relationship where a quantity changes at a rate proportional to its current value.

Question 2

The law of radioactive decay

Answer 2

• The probability per unit time that a nucleus will decay is constant, independent of time
• This constant is called a decay constant denoted by lambda λ
• It describes the number of nuclide that decays per unit time
• It is inversely proportional to a nuclide’s half life

Question 3

How is nuclear disintegration measured

Answer 3

• Is measured easily by measuring the effects nuclear disintegrations by counting the gamma rays with a suitable detector.

Question 4

Define half-life.

Answer 4

• The length of time it takes for a radioactive substance to decrease by half of its original value.

Question 5

Applications of exponential law in radiography.

Answer 5

(a) In nuclear medicine, radionuclides are used in diagnostic imaging and treatment of disease

(b) Attenuation of electromagnetic radiation by matter

Question 6

Examples of radioactive isotopes used in nuclear medicine.

Answer 6

• technetium-99m (Tc-99m)
• radioactive iodine
• strontium

Different radioactive isotopes are used depending on the type of test and the tissue or organ being studied,

Question 7

Explain the process of nuclear medicine.

Answer 7

• A patient is given radioactive substance it can be by injection
• As the radionuclide travels in the body it emits radiation during its decay
• A gamma camera is used to trace it with a signal
• The signal in obtained and transformed into an image (diagnosis) or the emitted radiation used to kill cancer cell

Question 8

(b) Attenuation of electromagnetic radiation by matter

Answer 8

• When electromagnetic radiation interacts with matter it can pass through, get absorbed or deflected
• Exponential law describes in quantitative terms the relationship between attenuation of the radiation and the thickness of the absorber
• Equal thicknesses of the absorber transmits equal fractions of intensity of radiation incident upon them
• Equal changes of thickness of absorber produce the same fractional change of the transmitted x-ray intensity

Question 9

Half-Value thickness

Answer 9

Is that thickness of substance which will transmit exactly one half of the intensity of the radiation incident upon it