Film is rearranged metal particles on tape which are read by an electromagnet. CDs are discs with burned pits in them which are read by a laser. What makes one analog and one digital?
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Audio tape contains varying degrees of magnetism. It is a lot like turning a dial on an adjustable light. Because the amount of magnetism at a certain spot is measured “as is”, and then comes out of the speakers as an analog signal.
The different between an analog and a digital signal is that a digital digital has a certain number of levels it can be at. These are numbered, and depend on how many bits (1s or 0s) you use. I5 totems or that if you write out as many 2s as you have bits, it tells you how many levels it has.
A bit is a 1 or a 0, but it can also be an off or an on, or any two choices. For a CD, the choices are “laser reflected into sensor” and “laser not reflected into sensor”. Writable CDs change the color on the CD so that it absorbs or reflects the light because it’s transparent and lets light through. Grooves work because the laser bounces off a different height, and misses its target.
These offs and one, 1s and 0s, are then grouped together into chunks. For 8 bit Audio, the chunks are 8 bits wide, etc.. These 1s and 0s are then converted into sound.
This is rarely done directly, but is in some cases like files that end in “.wav”. Mp3s on the other hand, read the CD as a bunch of code. It contains less data because it turns out that you can get really close to the original sound by using techniques like “wavelets”, which you can think of as digital bells all combining together to make your song.
But long story short, analog stuff is a range that is measured directly, and digital data can be written as bits, or numbers, or letters.
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