What is the least non zero thickness of a piece of glass with n=1.5, for which destructive interference of rod (650 nm) light in air can take place by reflection?

t = 108.33  nm

Explanation:

we know that for destructive interference we have following relation

for minimum thickness m =0

therefore we have

where

refrective index n = 1.5

putting all value to get required value of thickness

t = 108.33  nm

108.33 nm

Explanation:

For destructive interference the thickness , for minimum m=0

So  

Here is wavelength and n is order of index

So

So the least non zero thickness for destructive interference is 108.33 nm

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.