A thin film of refractive index $\mu =1.5$ and thickness $t=100\text{ nm}$ is illuminated by white light at normal incidence. Which wavelength $\lambda$ in the visible range $400\text{ nm}$ to $700\text{ nm}$ will be strongly reflected?

1. A.$400\text{ nm}$
2. B.$500\text{ nm}$
3. C.$600\text{ nm}$
4. D.$700\text{ nm}$