A Levels Physics (9702)•9702/12/M/J/22
Explanation
Electromagnetic Spectrum Frequency Ranges
Steps:
- Recall standard frequency ranges: microwaves (10^9–10^12 Hz), infrared (10^12–4×10^14 Hz), ultraviolet (7.5×10^14–10^16 Hz), X-rays (10^16–10^19 Hz).
- Note the given frequency: 2.5 × 10^14 Hz.
- Compare: 2.5 × 10^14 Hz exceeds microwave upper limit but falls below visible/UV threshold.
- Conclude it matches infrared range.
Why A is correct:
- Infrared region spans 10^12–4×10^14 Hz by definition, encompassing 2.5 × 10^14 Hz.
Why the others are wrong:
- B. Ultraviolet starts above 7.5 × 10^14 Hz, higher than given frequency.
- C. Microwave tops at 10^12 Hz, below given frequency.
- D. X-ray begins at 10^16 Hz, far above given frequency.
Final answer: A
Topic: Electromagnetic spectrum
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