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Centers for Disease Control and Prevention

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Effects of Electromagnetic Radiation on Health

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The Biological Effects of Electromagnetic Radiation on Human Health

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Effects of Electromagnetic Radiation on Human Health

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Electromagnetic Radiation (EMR) from Cell Phones, Computers, Tablets, Wi-Fi Routers and other personal electronic devices are harmful for human health in many ways. See this video and learn more on how the Radiation from these devices are harmful.

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5. If water depth is greater than 14 wavelengths, a progressive wave travels as a deep-water wave with a speed that is directly proportional to wavelength.

6. If water depth is less than 1/20 wavelength, the wave will move as a shallow-water wave, the speed of which increases with increased water depth.

7. As wind-generated waves form in a sea area, capillary waves with rounded crests and wavelength less than 1.74 centimeters (0.7 inches) form first. As the energy of the waves increases, gravity waves form, with increased wave speed, wavelength, and wave height.

8. Energy is transmitted from the sea area across the ocean by low, rounded waves called swell. Because swellsjnay move away from a number of storm areas in any ocean, it is inevitable that the swell from different storms will run together and the waves will clash or interfere with one another.

This gives rise to a special feature of wave motion interference pattern. An interference pattern is produced when two or more wave systems collide. This interference pattern is the algebraic sum of the disturbance that each wave would have produced individually.

The result may be a larger or smaller trough or crest depending on conditions. Thus, there are two types of interferences constructive and destructive.

Constructive interference occurs whenever and wherever a number of wave crests or troughs coincide and combine to produce a composite wave that is much larger than any of the individual wave components.

When there is extraordinary constructive wave interference, a wave of unusually large size for the prevailing wind conditions is created. This is called rogue Waves.

9. Swell releases its energy in the surf as waves that break in the shoaling water near shore. If waves break on a relatively flat surface, the result is usually a spilling breaker, whereas breakers forming on steep slopes have spectacular curling crests and are called plunging breakers. Others types of breakers are spilling, surging and collapsing.

10. The piace where the waves constantly and continuously break the water becomes foamy. This is called as surf zone after breaking some of the water moves towards the shore. This is called swash. The water that moves away from the shore into the sea at the bottom is called as backwash.

11. When swash is more powerful than backwash it builds and consequently is called constructive wave. When backwash is more powerful than swash it is called destructive waves.

12. Reflection of waves off seawalls or other barriers can cause an interference pattern called a standing wave. In standing waves, crests do not move laterally as in progressive waves but form alternately with troughs at locations called antinodes. Separating the antinodes are nodes, where there is no vertical movement of the water.

13. During storms, the combination of low air pressure and onshore winds may produce a storm surge that raises the water level at the shore many metres above normal sea level. Such surges are particularly destructive if they coincide with high tide.

14. Tsunamis, or seismic sea waves, are generated by seismic disturbances beneath the ocean floor. Tsunamis have been known to cause large scale damage and take tens of thousands of lives.

15. Internal waves are not well understood but are thought to form at density interfaces beneath the ocean surface, especially in connection with the pycnocline. They may be up to 100 metres (330 feet) high, with periods from 5 to 8 minutes.

16. Some waves that do not move horizontally but remain stationary are called Seiches. Such waves oscillate around a fixed point called a node.

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Article shared by Shally

1. Wave phenomena transmit energy through various states of matter by setting up patterns of oscillatory motion in the particles that make up the matter.

2. Most of the waves observed at sea are progressive wind waves, i.e., they are generated by winds. The distance over water, where the wind blows in a single direction is called as fetch.

3. Progressive waves are longitudinal, transverse, or orbital depending on the pattern of particle oscillation. Particles in ocean waves move primarily in orbital paths.

4. Characteristics used to describe waves are wave length (L), wave height (H), wave period (T), and wave speed (S).

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Electromagnetic waves are waves which can travel through the vacuum of outer space. Mechanical waves, unlike electromagnetic waves, require the presence of a material medium in order to transport their energy from one location to another.

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A crest (or peak) of a wave is one of the top-most parts, as high as the wave goes. A trough is the lowest part, as low as the wave goes. The amplitude of a wave is the vertical distance between the center line and a peak, or the center line and a trough.

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Reflected radio-wave amplitudes a proxy for varying temperatures?

Very low frequency (VLF) radio waves can be used to measure temperatures at the mesopause - the lower boundary of the upper atmosphere - according to researchers in Israel. This new method offers a cheaper and more comprehensive way of analysing the effects of long-term climate change on the upper atmosphere, as well as more short-term phenomena, such as solar storms or thunderstorms.

At the Earth's surface, increasing levels of greenhouse gases - such as carbon dioxide - reflect escaping infrared radiation back towards the ground. This results in a warming effect. In the upper atmosphere, however, greater concentrations of these gases have the opposite effect. At these low atmospheric densities, carbon dioxide primarily acts instead to radiate heat out to space - and does so more effectively at these altitudes than oxygen or nitrogen, the other main atmospheric components.

When the upper atmosphere cools, it also gradually shrinks - becoming denser and moving closer to the Earth's surface. This cooling also alters the propagation paths of radio waves, which pass through the upper atmosphere.

Clear correlations

The researchers' method works, therefore, by measuring the amplitude of VLF radio waves - which originate from navigational beacons - after they have bounced off the ionosphere, which contains the mesopause. The strength of the received signal is affected by the ionospheric density, which is in turn a product of the temperature. The team was able to observe a clear correlation between upper atmosphere temperatures - calculated from emissions from carbon dioxide measured by the TIMED satellite's SABER instrumentation - and the amplitude of the received radio waves.

"We have found a strong anti-correlation between the intensity/amplitude of low-frequency radio waves measured in our 'backyard' and changes in temperature of the upper atmosphere/lower ionosphere," paper author Colin Price, of Tel Aviv University, told physicsworld.com. "We found that a cooling/warming of the lower ionosphere (∼90 km altitude) causes an increase/decrease in the radio wave amplitude."

This new study adds considerably to our knowledge of the temperature changes in the upper atmosphere. While the primary driver of such fluctuations is the Sun - accounting for 60-70% of the variability - it was not previously possible to systematically measure the exact nature of the remaining shifts.

Cheap and continuous measurements

Previously, direct studies of mesopause temperatures had been difficult and expensive to undertake - with the region being both too low for in situ measurement by orbital satellites, and yet too high for aeroplanes or weather balloons. The team reports that its ground-based apparatus, however, is easy to use and considerably more cost-effective - with each VLF antenna and processing computer only costing around a few thousand dollars. The new method also allows for continuous measuring of a specific region of the upper atmosphere - a task that is not possible even with indirect measurements from orbiting satellites, such as NASA's TIMED mission.

Furthermore, the effect of greenhouse gases on the upper atmosphere is more pronounced than at ground level. Every one degree of warming in the lower atmosphere is met with a corresponding 10 degrees of cooling in the upper atmosphere. According to Price, this increased effect makes the impact of climate change easier to monitor.

More in-depth observations

"[This] discovery provides great potential of an economical approach for probing this mysterious atmosphere region in the global scale," comments Titus Yuan, a physicist at Utah State University, who was not involved in this study. He adds that the new methodology "could enable various critical scientific topics, such as the impact of global climate change in the upper atmosphere".

To solidify this work, the team is now looking into the possibility of taking more radio-wave observations - and for longer periods of time - from different locations around the globe. Their current study used radio stations located in Greece, Israel and New Zealand. In addition, the team is looking into comparing its results with other sources of temperature and solar-indices data.

The study is reported in the Journal of Geophysical Research: Atmospheres.

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Radio waves measure atmospheric temperature changes - Physics World

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Very low frequency (VLF) radio waves can be used to measure temperatures at the mesopause - the lower boundary of the upper atmosphere - according to researchers in Israel.

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A wave can be described as a disturbance that travels through a medium from one location to another location.

PARTS OF THE WAVE

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Transverse and Longitudinal Waves in Physics

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Parts of a wave are labeled for both transverse and longitudinal waves