Not sure but i will say D
Your answer is electricity, light and magnetism. They can be determined usinf elecromagnetic radioation.
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Even the energy can't be detected by our eyes, there are a lot of measurement instruments that can measure infrared (IR), gamma rays, radio or X-rays or ultraviolet (UV)</span>
Answer: 2940 J
Explanation: solution attached:
PE= mgh
Substitute the values:
PE= 10kg x 9.8 m/s² x 30 m
= 2940 J
Determine the frequency and the speed of these waves. The wavelength is 8.6 meters and the period is 6.2 seconds. Now find speed using the v = f. λ equation<span>.</span>