What is the smallest electromagnetic wave?

Answer 1

That depends on what you call "small".

-- Gamma rays are smaller than x-rays, but

-- x-rays are smaller than ultraviolet rays, but

-- ultraviolet rays are smaller than blue light waves, but

-- blue light waves are smaller than green, yellow, and orange light waves, but

-- any of those are smaller than red light waves, but

-- red light waves are smaller than heat waves, but

-- heat waves are smaller than radio waves.

Answer 2

X-rays, in the violet end of the spectrum.

Answer 3

It a thing I call goggle or bing or ask.com.

Answer 4

Cosmic rays have smallest wavelength