Charlie writes the steps shown to describe the use of a transistor in a closed circuit with flowing current.
using a transistor to amplify a signal
1. current (i1) flows from the base to the emitter.
2. an input causes a small increase in voltage across the base and emitter.
3. i1 increases a small amount.
4. current (i2) flowing from the emitter to the collector changes a large amount.
which change corrects the error in his steps?
change the title to “using a transistor as a switch.”
change step 1 to say that no current flows in the transistor at the start.
reverse the sizes of the changes in current in steps 3 and 4.
reverse the direction of current in step 4.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.