Explanation:

Introduction:
Arc welding is a welding process that uses an electric arc to join metal pieces together. During the welding process, various hazards are present, including intense glare, sparks, and harmful rays. Therefore, it is essential to protect the eyes from these hazards to prevent eye injuries and damage.

Protection against Intense Glare:
- During arc welding, an intense light is emitted from the welding arc, which can cause temporary or permanent damage to the eyes.
- The intense glare can lead to a condition known as arc eye or welder's flash, which is similar to a sunburn on the surface of the eye.
- Symptoms of arc eye include pain, redness, tearing, sensitivity to light, and a gritty feeling in the eyes.
- To protect the eyes from intense glare, welders wear specialized welding helmets or goggles with shaded lenses.
- The shaded lenses block out the bright light emitted by the welding arc, reducing the intensity of the glare and preventing eye damage.

Protection against Sparks:
- During arc welding, sparks are produced as a result of the high heat generated by the welding arc.
- These sparks can fly off and cause burns or injury to the eyes if they come into contact with the unprotected eyes.
- To protect the eyes from sparks, welders wear safety goggles that have a wrap-around design to provide complete coverage.
- The goggles are made of impact-resistant materials that can withstand the impact of flying sparks and debris.

Protection against Infra-red and Ultraviolet Rays:
- In addition to intense glare and sparks, arc welding also emits harmful radiation in the form of infra-red (IR) and ultraviolet (UV) rays.
- The IR rays can cause thermal burns to the eyes, while the UV rays can damage the cornea and the retina, leading to long-term vision problems.
- To protect the eyes from these harmful rays, welders wear helmets or goggles with lenses that have a specific shade number.
- The shade number indicates the level of protection provided by the lens against the UV and IR radiation.
- The higher the shade number, the darker the lens, and the greater the protection.
- The lenses are made of special materials that filter out the harmful UV and IR rays, allowing only safe levels of light to reach the eyes.

Conclusion:
In arc welding, eyes need to be protected against intense glare, sparks, and harmful infra-red and ultraviolet rays. Welders use specialized helmets or goggles with shaded lenses to protect their eyes from these hazards.