Aconvex lens is placed on a flat glass plate and illuminated from above with monochromatic red light. when viewed from above, concentric bands of red and dark are observed. what does one observe at the exact center of the lens where the lens and the glass plate are in direct contact?

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle

a skateboard rolling across the street - apex

i would say

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 =