6
Radiographic Testing Instructor Guide l LESSON 1
l 1012 =1 000 000 000 000 =1 tera (T)
Submultiples
1. Submultiples involve moving numerals to the right of the decimal point through use of exponents as
follows:
l 1/10 =10–1 =0.1
l 1/100 =10–2 =0.01
l 1/1000 =10–3 =0.001
2. Common prefixes involving submultiples and their symbols include:
l 10–3 =milli (m)
l 10–6 =micro (µ)
l 10–9 =nano (n)
l 10–12 =pico (p)
Multiplying with Exponents
For a common base in multiplication, exponents are added to get the result as in the following example:
23 × 22 =(2 × 2 × 2) × (2 × 2) =8 × 4 =32
or
23 × 22 =2(3 +2) =25 =32
Dividing with Exponents
1. The general principle for dividing with exponents is: px/py =p(x – y)
2. Thus, to find the value of 43/42, it can be calculated as:
43/42 =4(3 – 2) =41 =4
Logarithms
In radiographic testing, logarithms are essential for:
1. Estimating the activity of a radioisotope.
2. Determining the half-life of a radioactive source.
3. Calculating the half-value thickness of a source shield.
4. Determining proper exposure using a logarithmic scale or graph.
5. Computing the degree of darkness or optical density of a radiograph.
Logarithms — Summary
1. The use of logarithms can be summarized as follows.
l The log of any number to the same base is equal to 1 for example, log a a =1,
log e e =1, log
10 10 =1, and so on
Radiographic Testing Instructor Guide l LESSON 1
l 1012 =1 000 000 000 000 =1 tera (T)
Submultiples
1. Submultiples involve moving numerals to the right of the decimal point through use of exponents as
follows:
l 1/10 =10–1 =0.1
l 1/100 =10–2 =0.01
l 1/1000 =10–3 =0.001
2. Common prefixes involving submultiples and their symbols include:
l 10–3 =milli (m)
l 10–6 =micro (µ)
l 10–9 =nano (n)
l 10–12 =pico (p)
Multiplying with Exponents
For a common base in multiplication, exponents are added to get the result as in the following example:
23 × 22 =(2 × 2 × 2) × (2 × 2) =8 × 4 =32
or
23 × 22 =2(3 +2) =25 =32
Dividing with Exponents
1. The general principle for dividing with exponents is: px/py =p(x – y)
2. Thus, to find the value of 43/42, it can be calculated as:
43/42 =4(3 – 2) =41 =4
Logarithms
In radiographic testing, logarithms are essential for:
1. Estimating the activity of a radioisotope.
2. Determining the half-life of a radioactive source.
3. Calculating the half-value thickness of a source shield.
4. Determining proper exposure using a logarithmic scale or graph.
5. Computing the degree of darkness or optical density of a radiograph.
Logarithms — Summary
1. The use of logarithms can be summarized as follows.
l The log of any number to the same base is equal to 1 for example, log a a =1,
log e e =1, log
10 10 =1, and so on