Question

What condition for a dark fringe follows from \[\frac{a}{2}\sin\theta=\frac{\lambda}{2}\]?

Options

• \[a\sin\theta=\frac{\lambda}{2}\]

• \[a\sin\theta=2\lambda\]

• \[a\sin\theta=\lambda\]

• \[a\sin\theta=0\]

Answer 1

Multiplying both sides of \[\frac{a}{2}\sin\theta=\frac{\lambda}{2}\] by two gives \[a\sin\theta=\lambda\]. This is the condition for the first minima.