White light, with uniform intensity across the visible wavelength range of 400 nm - 690 nm, is perpendicularly incident on a water film, of index of refraction 1.33 and thickness 300 nm. At what wavelength (in nanometers) is the light reflected by the film brightest to an observer

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

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force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach

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 =