The photon flux of a one curie gamma ray source incident on a human tissue of cross-sectional area $1.0 \mathrm{~cm}^2$ decreases exponentially with tissue depth $x$
$I(x)=I_0 \exp (-\mu x)$
where $\mu$ is the attenuation constant and $I$ is the flux. Let $E=1 \mathrm{MeV}$ be the average energy of the incident gamma ray photon and $\sigma$ be the surface mass density of the tissue. Select the correct statement(s): (One curie is $3.7 \times 10^{10}$ disintegrations per second)

• A

  $E I_0$ is of order 0.1 Watt $/ \mathrm{m}^2$.
• B

  At a distance of $x=3 / \mu I$ is close to $0.37 I_0$.
• Correct answer
  C

  $E I / \sigma$ has dimensions of $\mathrm{L}^2 \mathrm{~T}^{-3}$.
• Correct answer
  D

  The attenuation constant for beta rays will be larger than that for photons of similar energy.

Hence, the correct answer is options: 'C', 'D'.