Which invisible rays can be utilized in beauty therapy?

The option that mentions infra-red and ultra-violet rays is recognized in beauty therapy due to their specific therapeutic and aesthetic benefits. Infra-red rays are commonly used in treatments for their ability to penetrate the skin, providing warmth that can aid in muscle relaxation, improve circulation, and enhance skin detoxification. These rays can also help alleviate pain and reduce inflammation, making them valuable in various beauty and wellness treatments.

Ultra-violet rays, on the other hand, are often associated with skin treatments like phototherapy, which can be beneficial for conditions such as psoriasis and acne. They also play a crucial role in the tanning process, allowing for controlled exposure that can enhance skin appearance when managed properly.

The other options fall outside the typical practices employed in beauty therapy. For example, while X-rays and gamma rays are not utilized due to their potential health risks and high energy levels, microwaves and radio waves are more associated with medical imaging and telecommunications, not direct beauty applications. Laser beams and radio frequencies do have their place in some aesthetic treatments, but it's the specific therapeutic qualities of infra-red and ultra-violet rays that make them particularly useful in this context.