wavelength

definition: 
The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave:
sentence: 
Unfortunately, Earth's atmosphere blocks almost all wavelengths in the electromagnetic spectrum. The most powerful telescopes in the world, spanning all wavelengths of the electromagnetic spectrum, were retooled and reprogrammed to observe the dying star. Visible light consists of a ‘rainbow’ or spectrum of electromagnetic waves of different wavelengths.
difficulty: 
very easy
toefl frequency: 
2
toefl classification: