Physics and Interactions Flashcards

Bremsstrahlung radiation efficiency increases with:

Answer: Higher atomic number (Z) of the target and higher electron energy

Bremsstrahlung production is proportional to Z² and to the electron kinetic energy, so high-Z targets (like tungsten) and high-energy electrons maximize bremsstrahlung yield.

The mass attenuation coefficient (μ/ρ) of a compound material can be calculated using:

Answer: The mixture rule: sum of weight-fraction-weighted elemental coefficients

The mixture rule states that μ/ρ for a compound equals the sum of each element's weight fraction multiplied by its elemental mass attenuation coefficient.

Which quantity is conserved in all nuclear reactions?

Answer: Total baryon number and charge

Conservation laws in nuclear reactions require that total baryon number (A) and electric charge (Z) are conserved, along with energy and momentum.

Positron annihilation produces two photons, each with an energy of:

Answer: 0.511 MeV traveling in opposite directions

When a positron annihilates with an electron, two 0.511 MeV photons are emitted in opposite directions (180° apart) to conserve momentum.

The range of alpha particles in tissue is approximately:

Answer: A few tens of micrometers to ~100 μm

Alpha particles (4–8 MeV) have very short ranges in tissue, typically a few tens to about 100 micrometers, due to their large charge and mass causing dense ionization.

In the Compton effect, the energy of the scattered photon is LOWEST when the scattering angle is:

Answer: 180°

At 180° (backscatter), the photon transfers maximum energy to the recoil electron, leaving the scattered photon with the lowest possible energy.

Which type of radiation has the greatest penetrating power in matter?

Answer: High-energy gamma rays

High-energy gamma rays are highly penetrating because they are uncharged photons that interact only probabilistically; thick dense shielding is required to attenuate them significantly.