A thin film of oil $(n_o = 1.50)$ with varying thickness floats on water $(n_w = 1.33)$. When it is illuminated from above by white light, the reflected colors are as shown in Fig. 24–60. In air, the wavelength of yellow light is 580 nm.
- Why are there no reflected colors at point A?
- What is the oil’s thickness $t$ at point B?
Source: Giancoli, Douglas C., Physics: Principles with Applications, 7th Edition, 2014.
- A half wavelength phase shift occurs due to reflection at the air-water interface, and oil thickness is so small that it doesn't add any significant phase shift.
- 290 nm