You are standing in air and are looking at a flat piece of glass (n = 1.52) on which there is a layer of transparent plastic (n = 1.61). Light whose wavelength is 595 nm in vacuum is incident nearly perpendicularly on the coated glass and reflects into your eyes. The layer of plastic looks dark.

Find the smallest possible nonzero value for the thickness of the layer.

184.78 nm

Explanation:

The condition for dark fringes in thin film surrounded by air is given by the following relation:

2nt = mλ

The order number of the dark fringe is m=1.

Calculate the smallest possible non zero value for the thickness of the layer is,

2nt = mλ

t = mλ / 2n

= (1) (595 * 10⁻⁹m) / (2) (1.61)

= 1.8478 * 10⁻⁷ m

= 184.78 nm

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =