Question #43572

A monochromatic plane wave of wavelength $\lambda = 600 \text{ nm}$ (in vacuum) is incident on an opaque screen containing two identical circular pinholes. The plane of incidence contains the centers of the two pinholes, and the incident light rays make an angle $\theta_0$ with the normal to the screen, where $\sin \theta_0 = 0.75$. The diameter of each pinhole is $a = 1.22 \text{ } \mu\text{m}$ and the distance between their centers is $d = 4.00 \text{ } \mu\text{m}$. The entire setup is immersed in a transparent liquid of refractive index $\mu = 1.5$. The interference pattern is observed on a large semicircular screen placed in the forward direction in the plane of incidence, covering observation angles $-\pi/2 \le \theta \le \pi/2$ (where $\theta$ is measured from the normal). How many interference principal maxima of non-zero intensity are observed on the screen strictly within the central diffraction envelope (Airy disk) of the individual pinholes?