The human circulation system has approximately 1 × 109 capillary vessels. each vessel has a diameter of about 8 μm .assuming the cardiac output is 5 l/min, determine the average speed, in centimeters per second, of blood flow through each capillary vessel.

To solve this exercise we must apply the concept of Flow as the measure given to determine the volume of a liquid flowing per unit of time, and that can be calculated through velocity and Area, mathematically this can be determined as

Q = Discharge of Flow

A = Cross sectional Area

Velocity

The area of the cross section of the capillary tube is

The total Area by this formula:

Where,

Stands for area of capillary

n = Stands for number of blood vessels

Finally replacing at our first equation,

Therefore the average speed, in centimeters per second, of blood flow through each capillary vessel is 1.66cm^3/s

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.