Electromagnetic spectrum wavelength order

Steps:

• Recall EM spectrum: x-rays shortest (~0.01-10 nm), visible light next (400-700 nm), microwaves/radar (cm to m), radio waves longest (>1 m).
• Assign to sources: 2 (x-rays) <10 nm; 4 (LED light) 400-700 nm; 3 (radar) exactly 30 m; 1 (radio transmitter) typically >30 m (e.g., AM/FM bands).
• Compare: 2 shortest, then 4, then 3 at 30 m, then 1 longest.
• Sequence increasing wavelength: 2→4→3→1.

Why C is correct:

• Matches EM spectrum progression where wavelength increases from x-rays to visible to radar to radio waves.

Why the others are wrong:

• A and B: Start with radio (1, long) before x-rays (2, short), reversing order.
• D: Places radar (3, 30 m) before radio (1, longer), incorrect.

Final answer: C