The different signal bands of radiation detected by a receiver are electromagnetic waves. In a vacuum, all of these waves must have:
When the receiver is active and registering a signal, it shows that:
The receiver requires a minimum current to flow to register a detection. A student investigates this using the circuit shown below.
State how an ammeter should be connected to the circuit to measure the current passing through the photodiode.
The student records the minimum power threshold at which different electromagnetic bands register a signal:
| Band of electromagnetic spectrum | Minimum power threshold in mW\text{mW}mW |
|---|---|
| Radio waves | 45.2 |
| Microwaves | 28.5 |
| Infrared | 12.1 |
| Green Light (Visible) | 4.8 |
| Ultraviolet | 1.5 |
Determine whether a bar chart or a line graph is more appropriate to display these results. State what should be plotted on each axis.
The student concludes:
"The minimum power threshold required to register a signal decreases as the frequency of the radiation increases."
Evaluate the student's conclusion using the data in the table and your knowledge of the electromagnetic spectrum.
