What is a scalar? apex
a. a measurement of displacement.
b. the direction of a vector.
c. a quantity that does not indicate direction.
d. a magnitude and a direction.

C. A quantity that does not indicate direction.

Explanation:

There are two types of quantities in physics:

- Scalars: a scalar quantity is a quantity which has only a magnitude, and not a direction.

Examples of scalar quantities are: mass, temperature, time, distance, speed...

- Vectors: a vector quantity is a quantity having both a magnitude and a direction.

Examples of vector quantities are: velocity, displacement, force, acceleration...

Therefore, for the question in the problem:

What is a scalar?

The correct answer is:

C. A quantity that does not indicate direction.

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.

force tends to be low and long diustance masses are high