Question

In solar cells a silicon solar cell (μ = 3.5) is coated with a thin film of silicon monoxide SiO (μ = 1.45) to minimize reflective losses from the surface. Determine the minimum thickness of SiO that produces the least reflection at a wavelength of 550 nm, near the centre of the visible spectrum.

Answer 1

The reflected light is a minimum when rays 1 and 2 (shown in figure) meet the condition of destructive interference.

Note : Both rays undergo a 180° phase change upon reflection. The net change in phase due to reflection is therefore zero, and the condition for a reflection minimum requires a path difference of λ_μ/2. Hence,