This is a summary of the inventions I learned about in lessons one hundred fifty-one through one hundred fifty-four.

In lesson one hundred fifty-one, I studied the invention of the electron microscope. In 1933, Ernst Ruska invented the electron microscope. Instead of using light, electron microscopes use a beam of electrons to magnify objects. The object being blasted with electrons will absorb some of them, and those absorbed electrons cause it to emit even more. These new electrons are then converted into light, and an image is formed. Much smaller objects, including germs and atoms, can be seen with the electron microscope than with other microscopes.

In lesson one hundred fifty-two, I learned about the invention of FM radio. FM radio was invented by Edwin Armstrong in 1933. FM radio doesn’t pick up as much noise from electronics and thunderstorms than AM radio does because AM radio works using amplitude modulation. The amplitude can easily be altered by natural causes, so the sound quality wasn’t very good. FM radio, however, works using frequency modulation.

In lesson one hundred fifty-three, I studied the invention of nuclear fission. Nuclear fission was discovered by Otto Hahn and Fritz Strassmann in 1938, and consists of splitting atoms into smaller atoms using neutrons, starting a chain reaction. This creates a ton of energy, so nuclear fission is used as a source of power in nuclear power plants.

Last of all, I learned about the invention of the transistor in lesson one hundred fifty-four. Before the transistor, there were vacuum tubes, but these were inefficient and unreliable. It took too many too often to power computers, especially as they got more powerful. A solution to this problem was needed, and it came in the form of the transistor.

The transistor was invented in 1946 by John Bardeen, William Shockley, and Walter Brattain. Transistors have three parts called the base, the emitter, and the collector (also known as the source, the gate, and the drain). When the base is connected to a positive source and the collector to a negative source, the transistor is off. When the emitter is touched to the collector, the transistor is turned on. This is because no electrons can flow through the circuit when it’s negatively charged. Transistors can be used as switches or amplifiers, and are found in pretty much every electronic device.

Thinking back to 1950, I don’t believe anyone thought technology would have progressed so much by 2000. Fifty years from today, and we’ll probably be much more reliant on technology. Transistors most likely won’t exist anymore, and new technology will take its place.