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Physics · Class 12

Electromagnetic spectrum

Electromagnetic Waves

Move continuously from radio to gamma rays. Frequency increases as wavelength decreases; photon energy rises with frequency. Spectrum boundaries are conventional and overlap between sources and uses.

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Electromagnetic spectrum

ரேடியோ முதல் காமா வரை அதிர்வெண் உயரும்போது அலைநீளம் குறையும். ஒளித்துகள் ஆற்றல் hf ஆகும்.

Key notes, relationships and model limits

Key relationship

λ=c/f; Ephoton=hf.

Remember

Move continuously from radio to gamma rays. Frequency increases as wavelength decreases; photon energy rises with frequency. Spectrum boundaries are conventional and overlap between sources and uses.

Common trap

Increasing frequency shortens vacuum wavelength and increases photon energy. Spectrum boundaries are conventional approximate ranges.

Model limits

Vacuum wavelength; approximate conventional band boundaries. Typical uses: radio communication, microwave links/heating, infrared thermal sensing, visible vision, UV fluorescence, X-ray imaging, gamma nuclear spectroscopy.

What you will learn

Use the controls and plotted relation to explain electromagnetic spectrum.

Try the experiment

Try both scenarios, change one control, and predict the result before checking the graph and readouts.

Think of it this way

Change one input while keeping the others fixed, as you would in a controlled experiment.

Worked example

At f=10¹⁴ Hz, λ≈3 µm and photon energy≈0.414 eV (infrared).

Why this matters

The model connects electromagnetic spectrum with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

Higher frequency electromagnetic radiation has?

Read the explanation

Shorter wavelength and greater photon energy.

Course connection: Class XII Chapter 8. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.