Interstellar space (far from any stars) contains atomic hydrogen (h) with a density of 1 atom/cm3 and at a temperature of about 2.7 k. determine (a) the pressure in interstellar space, (b) root-mean square speed of the atoms and (c) the kinetic energy stored in 1 km3 of space.

Explanation:

Given that,

Number density

Temperature = 2.7 K

(a). We need to calculate the pressure in interstellar space

Using ideal gas equation

The pressure in interstellar space is

(b). We need to calculate the root-mean square speed of the atom

Using formula of rms

Put the value into the formula

The root-mean square speed of the atom is 258.6 m/s.

(c). We need to calculate the  kinetic energy

Average kinetic energy of atom

Where, k = Boltzmann constant

Put the value into the formula

The kinetic energy stored in 1 km³ of space is .

Hence, This is the required solution.

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.