Day and night duration- due to refraction or scattering?

Many students have this doubt and they questioned their teachers whether the duration of day and night is due to refraction or scattering of light? And also, there is a big debate among the physics teachers, some of them supported refraction of light and some supported scattering of light. In this post, let’s clarify this question.

        If we look into in this matter, the day and night duration is neither due to refraction nor due to scattering of light. This phenomenon is purely geographical. The duration depends upon rotation of earth about its axis, revolution around sun, inclination of its axis with the plane of the motion of earth and our location on the earth.

Greenland, Norway, Alaska, finland are some countries where nights and days do happen in very long duration. Earth’s rotation causes the period of day and night. The part facing the sun is in daylight and other facing away is in darkness. Earth rotates about its axis (imaginary line). Earth’s axis is not perpendicular. There is an axial tilt of 23.5°. Due to this tilt, the sun shines at different angles on different latitudes. That’s why areas coming under arctic circle experiences 6 month day in northern hemisphere and 6 month night in southern hemisphere. The axial tilt of earth decides the duration of day and night at different locations on earth.

Some people also comments that the refraction and scattering does increases duration of day as compared to night time. But still both these phenomena do not play much role.

Before sun rises, we still see the light of sun, this is due to refraction of sunlight with the atmosphere of earth. When light touches the atmosphere, its bends due to refraction and we able to see the light before the sun rises. Same with the scattering also, particles present in the atmosphere scatters light and we experience light before the sun rises. Both these phenomena add 3 to 4 min in duration of day but doesn’t mean elongation of day than night. This thing explains by geographical concepts.