In interference, two individual amplitudes are `A_0` each and the
intensity is `I_0` each. Find resultant amplitude and intensity at a point, where:
(a) phase difference between two waves is `60^@`.
(b) path difference between two waves is `lambda/3`.

Explanation

To solve the problem, we need to find the resultant amplitude and intensity at a point where the phase difference between two waves is \(60^\circ\) and where the path difference is \(\lambda/3\).

### Step-by-Step Solution:

**Given:**
- Individual amplitude of each wave, \(A_0\)
- Intensity of each wave, \(I_0\)
- Phase difference, \(\phi = 60^\circ\) for part (a)
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