A Level Physics Practice Exam

What does the variable 'd' represent in the diffraction grating equation?

1. The distance to the screen

2. The separation of the grating slits

3. The wavelength of the light used

4. The diameter of the grating

The correct answer is: The separation of the grating slits

In the context of the diffraction grating equation, the variable 'd' specifically represents the separation of the grating slits. This is a crucial element in understanding how diffraction patterns are formed when light encounters a grating. The spacing between the slits influences the angles at which light constructsively and destructively interferes, leading to distinct patterns of light and dark spots on a screen. The diffraction grating equation, typically expressed as \(d \sin \theta = n\lambda\), illustrates that 'd' directly affects the sin value for a given angle, thereby determining the position of the interference maxima. As the separation between the slits increases, the angles for the maxima change, which is fundamental to predicting the locations of the bright fringes in a diffraction pattern. This relationship allows for practical applications in determining the wavelengths of light and analyzing the properties of light sources.