Final answer:
Only minimal levels of laser radiation are not considered hazardous. Exposure to alpha, beta, and gamma radiation varies in how it affects the human body, with higher doses being lethal and smaller doses possibly resulting in long-term health issues. Ultraviolet light is potentially harmful but is mostly filtered by the Earth's ozone layer.
Step-by-step explanation:
The question is concerned with the safety levels of laser radiation. Only minimal levels of radiation are not considered hazardous to human health. Alpha radiation, for instance, has a very short range and cannot penetrate the skin's dead layers, making it relatively safe unless ingested or inhaled. Beta radiation can be more harmful as it penetrates skin and can cause damage, but it can be shielded with materials like lead. Gamma radiation has a much greater range and can pass through human bodies, but can be reduced to safe levels by shielding. Health risks from radiation include cancer and genetic changes. Still, there is a concept known as hormesis that suggests low levels of radiation might even be beneficial by stimulating repair mechanisms in cells.
Radiation doses of 600 rem are fatal, whereas doses of 500 rem are lethal to 50 percent of exposed subjects within 30 days. Smaller doses, such as those below 50 rem, are less immediately harmful but may cause long-term issues. Under 100 mrem per year, which is typical for artificial sources, presents even less risk, though still not entirely negligible. Notably, ultraviolet light, which is higher in frequency than visible light, can cause a variety of harmful chemical reactions in organisms, yet it is largely filtered out by the ozone layer in our atmosphere.