Final answer:
To protect the farm workers from UV rays, John should provide them with sun protective clothing, protective eyewear, and encourage the use of sunscreens.
Step-by-step explanation:
To protect the farm workers from UV rays, John should provide them with sun protective clothing that has a UPF rating to block UVA and UVB rays. Additionally, he should provide protective eyewear that covers the full eye area and blocks UV radiation. It is important to note that ordinary glasses provide some protection, but most plastic lenses offer more protection than glass lenses. Lastly, John should ensure that the farm workers are well-informed about the risks of UV exposure and encourage them to use sunscreens with a high SPF that protect against both UVB and UVA radiation.