10. which of the following statements is accurate?
a. sound waves passing through the air will do so as transverse waves, which vibrate vertically and still retain their horizontal
positions.
b. compressions and rarefactions occur throughout a transverse wave.
c. the wavelength of both traverse and longitudinal waves is measured parallel to the direction of the travel of the wave.
d. amplitude of longitudinal waves is measured at right angles to the direction of the travel of the wave and represents the
maximum distance the molecule has moved from its normal position.

Before coming into conclusion first we have to understand the nature of longitudinal wave and transverse wave.

The longitudinal wave is a type of mechanical wave in which the direction of wave propagation is parallel to the particle vibration.In such type of wave one will notice compressions and rarefactions.

Compressions are the high pressure zones where the particles are very close to each other and rarefactions are the low pressure regions where there is  large separation between particles. Hence a longitudinal wave is a series of compresions and rarefactions.

The wavelength of a longitudinal  wave is the distance between two successive compressions or rarefactions. Hence the wavelength is measured parallel to the direction of wave.  As the particle vibration is parallel to wave propagation ,so the amplitude of the wave is measured parallel to wave direction.

Transverse wave is such type of mechanical wave in which the particle vibration is perpendicular to wave propagation.Here crests and troughs are formed.

The distance between two successive crests or troughs are called wavelength which is measured parallel to the wave propagation. As the particle vibration is perpendicular to wave propagation,so the amplitude of the wave is measured perpendicular to the wave propagation.It is so because  amplitude of the wave is the maximum distance travelled by the particle from equilibrium position.

Out of the four options given in the question only the option 3 is correct .Other options are wrong as violate the nature of longitudinal and transverse waves.

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.