The diagram is being used to illustrate the second law of thermodynamics, where qh represents a hot object and qc represents a cold object.

a black box on the left labeled q subscript h baseline and a touching white box on the right labeled q subscript c baseline.

which will best complete the diagram to illustrate the law?

adding in the boxes an arrow that points from qh to qc
adding in the boxes an arrow that points from qc to qh
adding in the boxes an arrow that points in both directions between qh and qc
adding in each box an arrow that points upward from qh and from qc

the correct answer is a. adding in the boxes an arrow that points from qh to qc

Adding in the boxes an arrow that points from to .

Explanation:

According to the Second Law of Thermodynamics, the heat transfer occur from a higher temperature body to a lower temperature body.

So, applying the Second Law of Thermodynamics, the correct answer is the first one: Adding in the boxes an arrow that points from to ; because this direction is pointing the right one, it doesn't violate the second law of the thermodynamics, the heat is gonna go from to , and the arrow indicates that.

Remember that the problem states that is a cold object and is a hot object.

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.