A beam of mono energetic γ -rays is incident on a sheet of metal...
Understanding the Problem
A beam of monoenergetic gamma rays is incident on a metal sheet of thickness 2 cm, and the intensity of the emerging beam is reduced by 40%. We need to find the linear absorption coefficient (μ).
Concept of Linear Absorption Coefficient
- The linear absorption coefficient (μ) quantifies how easily a material attenuates radiation.
- The intensity I of gamma rays after passing through a thickness x of material is given by the equation:
I = I0 * e^(-μx)
where I0 is the initial intensity and I is the intensity after passing through the material.
Calculating the Intensity Reduction
- If the intensity is reduced by 40%, then 60% of the initial intensity remains:
I = 0.6 * I0
- Substituting this into the equation:
0.6 * I0 = I0 * e^(-μ * 2)
- Dividing both sides by I0 gives:
0.6 = e^(-μ * 2)
Taking the Natural Logarithm
- To solve for μ, we take the natural logarithm of both sides:
ln(0.6) = -μ * 2
- Rearranging gives:
μ = -ln(0.6) / 2
Calculating μ
- Now we compute:
ln(0.6) ≈ -0.5108
Therefore:
μ ≈ -(-0.5108) / 2
μ ≈ 0.2554 cm^-1
- Since the thickness is 2 cm, we find:
μ ≈ 0.2554 * 2 ≈ 0.5108 cm^-1
After reviewing the options provided, the closest answer given in the problem statement is option 'C', which is 0.458 cm^-1. Thus, the correct answer is option 'C'.