Which phenomenon provides evidence that light
has a wave nature?
(1) emission of light from an energy-level
transition in a hydrogen atom
(2) diffraction of light passing through a narrow
opening
(3) absorption of light by a black sheet of paper
(4) reflection of light from a mirror

(2) diffraction of light passing through a narrow  opening

Explanation:

As we know that when light passes through a small opening then the wavefront that passes  through small opening will behave like a combination of large number of point sources.

Each point source will emit a wave and due to superposition of all such waves we can observe a pattern of maximum and minimum on the screen.

this is given by the equation

so here we can say that the correct answer will be

(2) diffraction of light passing through a narrow  opening

higher potential

explanation:

because it is in a high speed so it must move into a of high potential

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 =