Radioactive Iodine refers to a radioisotope of iodine that has an unstable nucleus, which means it emits radiation as it decays. This type of iodine is often used in medical procedures and treatments for conditions such as hyperthyroidism or thyroid cancer. When ingested or administered through other methods, the radioactive iodine can target and destroy overactive or cancerous cells in the thyroid gland without harming surrounding healthy tissue. The radiation emitted by the radioactive iodine is primarily in the form of beta particles which have a short range but high penetration power, making them effective at treating conditions within the body while minimizing damage to other organs and tissues.