Interference occurs when two coherent light waves superpose, with their resultant amplitude governed by the superposition principle. For interference between two coherent sources, the conditions for constructive and destructive interference are: (i) Constructive Interference:This requires the amplitudes of the two waves to add. It occurs when the path difference between the waves is an integer multiple of the wavelength:\[\Delta l = n \lambda \quad \text{where} \quad n = 0, 1, 2, 3, \dots\]Here, \( \Delta l \) is the path difference, \( \lambda \) is the wavelength, and \( n \) is an integer. (ii) Destructive Interference:This occurs when the amplitudes of the two waves cancel each other. It happens when the path difference is an odd multiple of half the wavelength:\[\Delta l = \left( n + \frac{1}{2} \right) \lambda \quad \text{where} \quad n = 0, 1, 2, 3, \dots\]Here, \( \Delta l \) is the path difference, \( \lambda \) is the wavelength, and \( n \) is an integer. Application to Two Sodium Lamps:Two sodium lamps typically do not produce coherent light. The light from each lamp contains multiple wavelengths, resulting in a broad spectrum rather than a single frequency and phase relationship. Coherence is essential for interference.Because sodium lamps emit a mix of wavelengths, they are unsuitable for generating interference patterns that require coherent sources like lasers. Consequently, the conditions for constructive and destructive interference are not readily applicable to light from two sodium lamps. Conclusion:While the principles of constructive and destructive interference are well-defined based on wavelength, their practical application to light from two sodium lamps is limited due to the lack of coherence in the emitted light.