A

Step 1: Understand the formula for angular fringe width in Young's double slit experiment. The angular fringe width (B8) can be calculated using the formula:

$$ heta = \frac{\lambda}{d}$$
where:

• \(\theta\) = angular fringe width
• \(\lambda\) = wavelength of light
• \(d\) = separation between the slits

Step 2: Convert the wavelength into meters. Given: \(\lambda = 6000 \text{ Å} = 6000 \times 10^{-10} m = 6.0 \times 10^{-7} m\)

Step 3: Plug in the values into the formula. Here, \(d = 3.0 \times 10^{-3} m\)

$$\theta = \frac{6.0 \times 10^{-7}}{3.0 \times 10^{-3}}$$

Step 4: Calculate the angular fringe width:

$$\theta = 2.0 \times 10^{-4} ext{ radians}$$

Therefore, the angular fringe width is approximately:
$$\theta = 2.0 \times 10^{-4} ext{ radians}$$