The size distribution of the powder particles used in Powder Metallurgy process can be determined by

The correct option is Laser scattering.

Powder metallurgy is a metal-processing technology in which parts are produced from metallic powders. The size and distribution of these powder particles are critical parameters because they directly influence the flowability, compressibility, and sintering behavior of the powder, which ultimately affects the properties of the final component.

Particle size distribution is widely determined using the technique of laser diffraction, also commonly referred to as laser scattering. Let us understand the step-by-step physical principles of how this method works:
1. Light-Particle Interaction: When a laser beam passes through a dispersed particulate sample, the particles scatter the light.
2. Scattering Angle and Particle Size: According to the principles of light scattering (such as Mie scattering theory and Fraunhofer diffraction), the angle at which the light is scattered is inversely proportional to the particle size.
Specifically, larger particles scatter light at narrow angles relative to the laser beam, whereas smaller particles scatter light at wider angles. This relation can be represented as:
$$\theta \propto \frac{1}{d}$$
where $\theta$ is the scattering angle and $d$ is the particle diameter.
3. Intensity and Quantity: The intensity of the scattered light at any given angle is related to the number of particles of that specific size.
4. Detection and Analysis: A series of photosensitive detectors measure the angular distribution of the scattered light intensity. Mathematical models then process this scattering pattern to calculate the volume-based size distribution of the powder particles.

Let us briefly look at why the other options are incorrect:
- Laser reflection: Reflection focuses on the light bouncing off surfaces and is generally used for surface roughness or distance measurement rather than determining size distribution of fine particles.
- Laser absorption: Absorption measures the energy taken up by the material, which is useful for chemical composition or concentration analysis but does not provide information about particle size.
- Laser penetration: Penetration (or transmission) measures the unscattered light passing straight through a medium, which alone cannot resolve the individual sizes of a distribution of particles.

Therefore, Laser scattering is the precise and standard physical phenomenon utilized to determine the particle size distribution in powder metallurgy.