WooHoo – The Khan Academy has an app…

The Khan academy is a fantastic resource – a source of simple explanations for many of the concepts we need at A level. https://www.khanacademy.org/science/physics/light-waves

Check out the app on the The App Store or Google Play.

While you are at it check out Brightstorm.com, Sixty Symbols and Dr PhysicsA Youtube channel.