State the conditions to get steady interference pattern.

Explanation

To achieve a steady interference pattern, the following conditions must be met:

1. **Coherent Sources**: The two sources of light (S1 and S2) must be coherent. This means they should have a constant phase difference and the same frequency. Coherence ensures that the waves from both sources maintain a consistent relationship over time, which is essential for producing a stable interference pattern.

2. **Small Slit Separation**: The distance between the two slits (d) should be small. A smaller slit separation allows for a greater path difference between the waves emanating from the two slits, which enhances the visibility of the interference fringes.

3. **Large Distance to Screen**: The distance from the slits to the screen (D) should be large. A larger distance helps in spreading out the interference pattern, making it easier to observe distinct bright and dark fringes.

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