The ability of electromagnetic waves to penetrate water depends on the frequency or wavelength of the waves. In general, water is relatively transparent to certain parts of the electromagnetic spectrum, while it absorbs or scatters others.
Radio waves and some microwaves can penetrate water to varying depths depending on their frequency and the water's properties. Lower frequency radio waves, such as those used for long-range communication, can penetrate water to a significant extent, sometimes reaching depths of several meters or more. However, as the frequency increases, the penetration depth decreases.
Microwaves in the range of a few gigahertz (GHz) can also penetrate water to some extent, but their penetration depth is generally limited to a few centimeters. This property is exploited in microwave ovens to heat water molecules within food.
As we move to higher frequencies, such as infrared, visible light, ultraviolet, X-rays, and gamma rays, water becomes increasingly absorbent. Infrared radiation can penetrate water to a shallow depth, while visible light is mostly absorbed within the top few meters of the water column. Ultraviolet (UV) radiation is absorbed even more rapidly, typically within the top few centimeters.
X-rays and gamma rays are highly absorbed by water and have very limited penetration depths, ranging from millimeters to centimeters. These high-energy electromagnetic waves are primarily used in medical imaging and industrial applications.
In summary, the penetration depth of electromagnetic waves in water varies depending on the frequency. Lower frequency waves like radio waves can penetrate to significant depths, while higher frequency waves like X-rays and gamma rays have limited penetration and are highly absorbed by water.