Light illuminating a pair of slits contains two wavelengths, 600 nm and an unknown wavelength. the 10th bright fringe of the unknown wavelength overlaps the 9th bright fringe of the 600 nm light.
1. what is the unknown wavelength?

unknown wavelength is 540 nm

Explanation:

given data

wavelengths =  600 nm

10th bright fringe overlap = 9th bright fringe of 600 nm

to find out

unknown wavelength

solution

we get  here first nth bright fringe from the central maximum at distance y

y = n ×   ...............1

and we have given 10th bright fringe overlap = 9th bright fringe of 600 nm

so here

10 × = 9 × 600 ×    

solve it we get

= 9 ×

= 540 nm

so unknown wavelength is 540 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.