Why is the sky blue?

The colour of the sky comes from sunlight scattering off of the air molecules (and to your eyes). Blue light gets scattered more than red light because it has a shorter wavelength, and so the light you see when you look at the sky appears blue.

This is also why the Sun appears red at sunset. When you look directly at the Sun, you're looking at the light which hasn't scattered. As it travels through the atmosphere the blue light is gradually removed. At noontime the light travels a shorter distance through the atmosphere so only a bit of blue light is removed, whereas at sunset the light travels longer (because of the angle) so more blue light is removed, making it redder.

Interestingly the light from the Sun is actually bluish white - but appears yellow for this reason!

Note thankfully this isn't in any A level syllabus as far as I know, but it is interesting and a very typical Oxbridge interview question.

AP
Answered by Alex P. Physics tutor

8382 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Can a projectile of speed 10m/s at an angle of 45° to the horizontal following a path perpendicular to a wall 8m away and 6m high reach beyond the wall? Justify your answer. Take g as 10m/s/s


Calculate the frequency of a simple pendulum of length 950 mm. Give answer to an appropriate number of significant figures.


When light above the threshold frequency of a metal is shone on the metal, photoelectrons are emitted. If the power of the light halves, are the maximum kinetic energy of the photoelectrons and/or the number of photoelectrons altered, and if so, how?


What is the optimum angle to throw a snowball for maximum horizontal displacement? (Ignore air resistance, assume the snowball is thrown level with the ground. The angle is measured from the ground up)


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences