Final answer:
In a double slit experiment, an interference pattern of bright and dark fringes is created, with the bright fringes' intensity being highest at the center. This is explained using the principle of interference, detailed by the equation d sin θ = mλ. The interference is formed by the superimposition of light waves emanating from both slits, creating a pattern with characteristics of both single- and double-slit interference.
Step-by-step explanation:
The student's question pertains to the interference pattern observed in a double slit experiment with low light levels. In this experiment, light is passed through two narrow slits (S₁ and S₂), which act as secondary point sources of light, to create an interference pattern on a screen. This pattern typically consists of a series of bright and dark fringes, with the intensity of the bright fringes being highest at the center and falling off at larger angles.
The interference pattern is explained by the equation d sin θ = mλ, where d is the separation between the slits, θ is the angle of the fringe from the central maximum, m is the order of the fringe (an integer value), and λ is the wavelength of the light used in the experiment. When the slits are closer together, this results in greater spreading of the bright fringes. The pattern observed is a combination of single- and double-slit characteristics; the evenly spaced bright spots can be attributed to double-slit interference, while the dimming of these spots on either side is a characteristic of single-slit interference. Furthermore, the spacing between the bright spots helps us to determine whether the slit width is smaller or larger than the separation between the slits.