What statement regarding radioactive fallout is incorrect?

The statement regarding radioactive fallout that is deemed incorrect is the assertion that severe damage would occur across the entire nation's area. Radioactive fallout occurs as a result of nuclear explosions or accidents and involves the dispersal of radioactive particles. The extent and severity of damage from such fallout depend significantly on various factors, including the size of the explosion, the altitude at which it occurs, weather conditions, and geographical features.

In many cases, the areas most severely affected are relatively localized, with damage decreasing with distance from the site of the explosion or contamination. Therefore, severe damage would not typically be uniform across an entire country but instead would vary based on proximity, environmental conditions, and other mitigating factors.

On the other hand, the statements about gamma radiation are accurate. Gamma radiation is indeed not detectable by human senses, meaning individuals cannot see, hear, or feel gamma rays. This characteristic necessitates the use of specialized instruments for detection and measurement, which is why gamma radiation is quantified in terms of roentgens, a unit that expresses exposure to radiation from gamma rays. These instruments are essential for assessing radiation exposure and determining safety measures in environments affected by radioactive materials.