Which of the two is scattered more easily: light of shorter wavelengths or light of longer wavelengths?

A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere.

(a) What does the student mean by saying that the sun can be seen after it has set?

(b) Do you think that the students' conclusion is correct?

What is the colour of the sunlight:

(a) scattered by the dust particles in the atmosphere?

(b) scattered by the air molecules in the atmosphere?

State whether the following statements are true or false:

(a) The scattering away of red light makes the sky appear blue during the day time.

(b) The scattering away of blue light makes the sun appear red at sunset.

What colour does the sky appear to an astronaut?