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


£22 /hr

Amilah C.

Degree: Physics with a year abroad (Masters) - Edinburgh University

Subjects offered:Physics, Maths+ 1 more


“Hi there, welcome to me page! About Me: I am currently studying Physics at the University of Edinburgh. From a young age, science has always been a passion of mine, and hopefully I can convey this in my tutorials. Previously, I found...”

£30 /hr

Henri F.

Degree: Aerospace Engineering MEng (Masters) - Bristol University

Subjects offered:Physics, Maths+ 4 more

Further Mathematics

“Aerospace Engineering PhD candidate in spacecraft control with 6 years of experience in tutoring. ”

£20 /hr

Anthony S.

Degree: Physics (Bachelors) - Newcastle University

Subjects offered:Physics, Maths


“I love physics and maths! And I love teaching them too! My tutorials are engaging and informative for all abilities, and will push those exam results up.”

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

How would you explain general relativity?

Describe and explain the photoelectric effect (6 marks)

How ideal gas density depends on temperature?

What are quarks?

View A Level Physics tutors

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