Question

Which equation equates the top-to-middle path difference to the value required for destructive interference?

Options

• \[a\sin\theta=\frac{\lambda}{2}\]

• \[\frac{a}{2}\sin\theta=0\]

• \[\frac{a}{2}\sin\theta=\lambda\]

• \[\frac{a}{2}\sin\theta=\frac{\lambda}{2}\]

Answer 1

The top-to-middle path difference is \[\frac{a}{2}\sin\theta\]. Setting it equal to \[\frac{\lambda}{2}\] makes corresponding rays cancel.