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Two-point Interference

Could you please explain the difference between anti-nodal and nodal lines in relation to two- point interference?

Hi

The anti-nodal line is a line when diffraction occurs, and two waves superimpose (meet at a point) in phase to each other (crest meets crest and Trough meets Trough). This creates a wave which a larger amplitude as the amplitudes of both the waves basically added. This is Known as Constructive Interference pattern. If a waves meet constructively in a line then it is known as an Anti-nodal line, However, when waves meet out of phase to each other, then the amplitudes of two waves decrease (This is because of the waves cancelling out). This is known as Destructive Interference Pattern. Just because the amplitudes of two waves cancel, this usually results in no wave observed at the point where waves have superimposed destructively. Thus, if this happens in a line, then it is known as Nodal line. The “No” in the word nodal can help you to know that there is no wave(s) in that line. Furthermore, the image below shows an Anti-nodal line as the blue and green waves meet in phase to each other. However, the nodal line will be between the anti-nodal lines as the waves meet out of phase to each other.

Thank you for your detailed answer.