Infrared rays are invisible, they have a much higher wavelength than visible light. Ultraviolet rays have a much lower wavelength than visible light. The higher the wavelength, the higher the energy. Hope that helps :)
We cannot visualize the organs or tissues inside of our body, but a biopsy helps in making a diagnosis by providing a piece of tissue for examination. Biopsies are often associated with cancer, but they can be used to diagnose other conditions and to see how far a disease has progressed.