Why does the rising and the setting sun appear red?

When the sun rises in the morning, it appears like a red ball. As the day advances, the colour appears white, but at the time of sunset in the evening, the colour again appears red. Do you know why it is so?

We know that the earth revolves round the sun. The part of the earth receiving the sunlight is lighted and we say it is day in that part. We also know that the white sunlight comprises seven colours-violet, indigo, bleu, green, yellow, orange and red in the morning and evening, when the sun is near the horizon, the rays have to travel a longer path in the atmosphere to reach us than in the noon. The distance travelled by the sun rays in the atmosphere in the morning and evening is fifty times more than that in the noon. The dust, smoke and water vapours present in the atmosphere scatter away these colours differently. Violet is scattered most and red is scattered least. Therefore, the amount of red light which reached our eyes is maximum. As a result the sun appears red while rising and setting.