3.10 understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space

The electromagnetic spectrum is a range of different frequency waves, one section of the spectrum is visible light (light we can see.) All of the waves in the electromagnetic spectrum travel at the same speed when they are in a vacuum.

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