A Level Physics Practice Exam

The equation \( n \cdot \text{wavelength} = d \cdot \sin X \) is derived from the principles of wave interference, particularly in the context of diffraction and the behavior of light waves passing through a grating or around obstacles. In this equation, \( X \) represents the angle of diffraction, which is crucial when analyzing how waves spread out after passing through a slit or around an edge.

When light encounters a diffraction grating or slit, it does not travel in a straight line; rather, it spreads out into different directions. The angle of diffraction is the angle at which a particular order of the wavefronts exit the grating relative to the original direction of the incoming wave. This angle is instrumental in determining the positions of bright and dark fringes in diffraction patterns observed in experiments such as the double-slit experiment.

Understanding the role of the angle of diffraction helps in analyzing various optical phenomena, while the other angles mentioned, such as incidence, reflection, and polarization, pertain to different physical processes and are not described by this specific equation. Thus, the correct interpretation of \( X \) as the angle of diffraction aligns perfectly with the foundational concepts of wave optics.