Explain
1 MRI and
2 X-ray
3 and Ultrasound

1)Magnetic resonance imaging (MRI) is a medical imaging technique that uses a magnetic field and computer-generated radio waves to create detailed images of the organs and tissues in your body. Most MRI machines are large, tube-shaped magnets.

2)An X-ray, or X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (30×1015Hz to 30×1018 Hz) and energies in the range 124 eV to 124 keV.

3)An ultrasound scan uses high-frequency sound waves to make an image of a person's internal body structures. Doctors commonly use ultrasound to study a developing fetus (unborn baby), a person's abdominal and pelvic organs, muscles and tendons, or their heart and blood vessels.

{HOPE IT HELPS}

3. dark matter

empty space could also be a simple vacuum