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

8169 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

why does photoelectric emission occur only when there is a certain threshold frequency of incident radiation?


What is escape velocity?


A car travelling at 28 m/s brakes until it stops completely after travelling a distance of 15 m. Calculate the deceleration of the car.


When a 470 micro farad capacitor is discharged through a fixed resistor R, the pd across it decreases by 80% in 45 s. Calculate the time constant of the circuit


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences