g We have studied diffraction from a single slit, where light is sent through a thin opening. A similar phenomena occurs when light bends around a thin object, like a human hair. Here the width of the hair plays the role of the width of the single slit. Measurements found that when a beam of light of wavelength 632.8 nm was shone on a single strand of hair, the first dark fringe on either side of the central bright spot were 5.22 cm apart. If the screen is 1.25 meters away, how thick was this strand of hair?

Explanation:

= Distance between central maxima and first minimum

m = Order = 1

d = Thickness of hair

= Wavelength = 632.8 nm

L = Distance between light source and screen = 1.25 m

Width of central maximum is given by

Distance between central maxima and first minimum is given by

Since is small

The strand of hair is thick.

b) phosphorus pentoxide

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 =