T0C02: Maximum permissible exposure: At which of the following frequencies

Q: At which of the following frequencies does maximum permissible exposure have the lowest value?

The correct answer is B: 50 MHz. The correct answer is B: 50 MHz. Maximum permissible exposure (MPE) has the lowest value at 50 MHz. RF exposure limits vary with frequency because the human body absorbs RF energy differently at different frequencies. Around 30-300 MHz (including 50 MHz), the body is most efficient at absorbing RF energy, so exposure limits are lowest (most restrictive) in this range. For amateur radio operators, this means you need to be especially careful with RF exposure on 6 meters (50-54 MHz) and nearby frequencies. Understanding this helps ensure compliance with RF safety regulations.

Updated: Dec 9, 2025 | Source: 2022-2026 Question Pool | Topic: T0C

T0C02T0C

At which of the following frequencies does maximum permissible exposure have the lowest value?

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Deep Dive: T0C02

The correct answer is B: 50 MHz. Maximum permissible exposure (MPE) has the lowest value at 50 MHz. RF exposure limits vary with frequency because the human body absorbs RF energy differently at different frequencies. Around 30-300 MHz (including 50 MHz), the body is most efficient at absorbing RF energy, so exposure limits are lowest (most restrictive) in this range. For amateur radio operators, this means you need to be especially careful with RF exposure on 6 meters (50-54 MHz) and nearby frequencies. Understanding this helps ensure compliance with RF safety regulations.

Why Other Answers Are Wrong

Option A (3.5 MHz): Incorrect. Lower frequencies (HF) have higher exposure limits because the body doesn't absorb HF energy as efficiently. Limits are less restrictive at HF. Option C (440 MHz): Incorrect. Higher frequencies (UHF) have higher exposure limits than the 30-300 MHz range. The body is less efficient at absorbing UHF energy. Option D (1296 MHz): Incorrect. Much higher frequencies (microwave) have even higher exposure limits. The most restrictive limits are in the 30-300 MHz range.

Exam Tip

Lowest MPE = 50 MHz. Think '5'0 MHz = '5'trictest limits. Around 30-300 MHz, body absorbs RF most efficiently, so exposure limits are lowest (most restrictive). HF and UHF have higher (less restrictive) limits.

Memory Aid

Lowest MPE = 50 MHz. Think '5'0 MHz = '5'trictest limits. Body absorbs RF most efficiently around 30-300 MHz, so exposure limits are lowest. Be especially careful on 6 meters.

Real-World Example

You operate on 6 meters (50-54 MHz) with 100 watts. The exposure limits are very restrictive at this frequency because your body efficiently absorbs RF energy in this range. You might need to maintain greater distance from your antenna or reduce power compared to operating on 20 meters or 70 cm, where limits are less restrictive.

Source & Coverage

Question Pool: 2022-2026 Question Pool

Subelement: T0C

Reference: 2022-2026 Question Pool · T0 - Safety

Key Concepts

Maximum permissible exposure RF exposure limits Frequency-dependent limits RF safety

Verified Content

Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T0C topic.