A light bulb emits the energy at a rate 16 n W. Treating the bulb as a point source, what is the irradiance at a distance of 2 m from the bulb? (Units in W/m2) Answer:

A light beam of wavelength λ= 500 nm, beam diameter 5 mm and intensity I is propagating in a medium. The absorption cross section of the medium is 2.3×10-19 cm-2 and upper-level lifetime is 10 µs. Calculate the power of the light beam that make the absorption coefficient of the medium (α) decays to 50% of its initial value (αo).

The x-ray linear attenuation coefficient of water at 40 keV is ?????? = 0.27 ??−1.The CT number of a tumor reported by a CT scanner is 60 HU. Calculate the linear attenuation coefficient of the tumor tissue ?

A material has a mass attenuation coefficient of 0.35 cm²/g (for a given photon energy) and has a density of 1 g/cm³. What is the thickness of the Half-Value Layer (HVL) of this material? (Note: the Half-Value Layer is the material thickness required to reduce an incident beam intensity by a factor of two).