Physics A Level
Chapter 12: Waves 12.8 Orders of magnitude
Physics A Level
Chapter 12: Waves 12.8 Orders of magnitude
Table 12.3 shows the approximate ranges of wavelengths in a vacuum of the principal bands that make up the electromagnetic spectrum. This information is shown as a diagram in Figure 12.15.
Here are some points to note.
- There are no clear divisions between the different ranges or bands in the spectrum. The divisions shown in Table 12.3 are somewhat arbitrary.
- The naming of subdivisions is also arbitrary. For example, microwaves are sometimes regarded as a subdivision of radio waves.
- The wavelength in the range $400 nm$ to $700 nm$ in free space (vacuum) are visible to the human eye.
Remember, $1\,nm = {10^{ - 9}}m$
- The ranges of X-rays and γ-rays overlap. The distinction is that X-rays are produced when electrons decelerate rapidly or when they hit a target metal at high speeds. γ-rays are produced by nuclear reactions, such as radioactive decay. There is no difference whatsoever in the radiation between an Xray and a γ-ray of wavelength, say, ${10^{11}}m$.
| Type of electromagnetic waves | Wavelength range / m |
| radio waves | $ \gt {10^6}$ to ${10^{ - 1}}$ |
| microwaves | ${10^{ - 1}}$ to ${10^{ - 3}}$ |
| infrared | ${10^{ - 3}}$ to $7 \times {10^{ - 7}}$ |
| visible | $7 \times {10^{ - 7}}$ (red) to $4 \times {10^{ - 7}}$ (violet) |
| ultraviolet | $4 \times {10^{ - 7}}$ to ${10^{ - 8}}$ |
| X-rays | ${10^{ - 8}}$ to ${10^{ - 13}}$ |
| γ-rays | ${10^{ - 10}}$ to ${10^{ - 16}}$ |
Questions
11) Copy Table 12.3. Add a third column showing the range of frequencies of each type of radiation.
12) Study Table 12.3 and answer the questions.
a: Which type of radiation has the narrowest range of wavelengths?
b: Which has the second narrowest range?
c: What is the range of wavelengths of microwaves, in millimetres?
d: What is the range of wavelengths of visible light, in nanometres?
e: What is the frequency range of visible light?
13) For each of the following wavelengths measured in a vacuum, state the type of electromagnetic radiation to which it corresponds.
a: $1 km$
b: $3 cm$
d: $5000 nm$
e: $50 nm$
f: ${10^{ - 12}}\,m$
14) For each of the following frequencies, state the type of electromagnetic wave to which it corresponds.
s: $200 kHz$
b: $100 MHz$
c: $5 \times {10^{14}}\,Hz$
d: ${10^8}\,Hz$