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.

Alex P. A Level Physics tutor, A Level Maths tutor, A Level Further M...

2 years ago

Answered by Alex, who tutored A Level Physics with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£20 /hr

William D.

Degree: Mechanical Engineering (Masters) - Leeds University

Subjects offered: Physics, Maths+ 2 more


“I am a British student currently in the first year of a masters degree in Mechanical Engineering at the University of Leeds. Having previously lived in Spain and Italy, I am fluent in both languages and have excellent communications s...”

£30 /hr

Louis S.

Degree: Mathematics (Bachelors) - Cambridge University

Subjects offered: Physics, Maths+ 6 more

Further Mathematics
Extended Project Qualification
-Personal Statements-
-Oxbridge Preparation-

“ second year undergraduate at the University of Cambridge, studying for a B.A. in Mathematics, having received A*s in A-Level Mathematics, Further Mathematics (Edexcel) and Physics (AQA)”

£24 /hr

Nathan L.

Degree: Materials Science (Masters) - Oxford, St Edmund Hall University

Subjects offered: Physics, Maths+ 1 more


“About Me: I'm a first year Materials science undergraduate at The University of Oxford. I loved learning about science and maths at school and hope my tutorials make you feel the same.  Structure: The key concept about tutorials i...”

About the author

£20 /hr

Alex P.

Degree: Physics (Masters) - Bristol University

Subjects offered: Physics, Maths+ 1 more

Further Mathematics

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

You may also like...

Other A Level Physics questions

A ball of mass 0.25 kg is travelling with a velocity of 1.2 m/s when it collides with an identical, stationary ball. After the collision, the two balls move together with the same velocity. How fast are they moving?

What speed do satellites orbit at?

What is the De Broglie wavelength of an electron given it has a kinetic energy of 1 eV? You are given the mass of an electron is 9.11x10^-31 kg and Planck's constant is 6.63x10^-34

Atmospheric Pressure is about 1.0x10^5 Pa. What is the downward force of the air on a desktop of surface area 1m^2?

View A Level Physics tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss