Physics
The waveform of a certain signal can be studied by

Cathode ray oscilloscope
Spectrometer
Sonometer
P – n junction diode

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Physics
Conservation of energy refers to the fact that

Energy cannot be created or destroyed but can be converted from one form to another
No chemical reaction is 100 percent efficient
The entropy of the universe is always increasing
If you conserve energy you will not be as tired

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