Electromagnetic waves and applications
Choose a type of radiation by connecting its properties with its use.
What you will learn
- Order the electromagnetic spectrum.
- Explain why X-rays can show bones.
One family of waves
Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays are electromagnetic waves. They are transverse and travel at the same speed in a vacuum. Across that order, frequency generally increases and wavelength decreases.
The wave equation connects speed, frequency and wavelength. If speed is fixed, a higher frequency means a shorter wavelength.
Match a property to a purpose
An application needs an explanation, not just the name of a wave. X-ray imaging relies on different tissues attenuating the radiation differently; bone generally absorbs more than surrounding soft tissue, producing contrast.
Higher-energy radiation can ionise atoms. That makes dose control relevant to imaging, but the exam skill here is explaining the connection between penetration, absorption and the resulting image.
Worked example
Why can an X-ray image distinguish bone from nearby soft tissue?
Show the worked solution
- Some X-rays pass through the body and reach a detector.
- Bone attenuates the radiation more strongly than much surrounding soft tissue.
- Different detector signals create contrast between the regions.
Answer Different absorption produces a visible contrast.
Common mistakes
- All electromagnetic waves have the same vacuum speed; X-rays are not faster than radio waves.
- Name the physical property that makes the chosen application possible.
What can you explain now?
At constant wave speed, what happens to wavelength if frequency doubles?
Compare with the explanation
It halves
Since v=fλ, a constant v requires λ to decrease by the same factor that f increases.
After trying it yourself, choose your next review. This is your self-assessment.
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