Question

which waves have the longest wavelength and the lowest energy on the electromagnetic spectrum?

Answer 1

The longer the wavelength the less energy it has. From higher to lower its: gamma, X-ray, ultraviolet, visible, infrared, microwave, and finally radio. Radio waves have both the longest wavelength and the lowest energy. Hopes that helps

Answer 2

UC18 is correct, and I wanted to tell you about an amazing fact related to this :D.
Some scientists in the UK run a super secure, super amazing x-ray lab, and they have a big track about 20 meters in diameter which electrons whizz around and around. There is a magnet placed around one point on the track, and when the electrons pass the magnet they emit x-rays. The scientists were able to focus the x-rays into a beam and they shot it through an 8 foot long treated wood (the type that looks like it has staples in it) beam, the LONG WAY and it made a clean hole all the way through! :D In comparison, if you shone a beam of visible light on a piece of wood like this, it would never penetrate it, although if you focus enough light into a small enough space you could burn it, but it would come nowhere close to the power of x-rays. :D