Wave propagation

Next Wave Propagation Wave Propagation.

Good Variable In general, radio frequencies below about 12 MHz or kHz are refracted by the layers Wave propagation gas which appear during the night, whereas frequencies above about 9 MHz or kHz are refracted by the layers of gas which appear during daylight.

Frequencies below about 5 MHz or kHz are largely absorbed by the day-time layers. The diagram on the right shows which frequencies generally are best for short-wave reception at different times of the day.

Above 12 MHz, conditions during the day are usually good but can be very variable especially as you climb higher in frequency: Although it is possible to generalise about how radio propagation will affect short-wave reception, the actual conditions will vary from day to day, month to month and from year to year.

The gases in the ionosphere are affected by the Sun's radiation and like the Earth, the Sun has weather which consists of storms as well as a winter and summer 'seasons' known as the Solar cycle. Whilst Solar storms are largely unpredictable, the Solar cycle can be tracked and takes 11 years to go from winter through summer and back to winter.

ADDITIONAL MEDIA

The weather on the Sun with respect to its effect on radio propagation is measured by counting 'sunspots'. These are areas of intense solar activity which come and go over the 11 year Solar cycle see the chart on the right which shows sunspot numbers for recent years.

When the sunspot count is high, higher frequencies will continue to propagate into the hours of darkness and even during the day, higher frequencies than normal will work. When the sunspot count is low, propagation is generally worse and focussed more on lower frequencies which can often become congested as broadcasters attempt to squeeze all of their transmissions into the lower frequency bands.

Help is at Hand Thankfully, help is at hand. All the hard work associated with interpreting the impact that Solar weather conditions are having on short-wave radio reception has been done for you.

The chart on the left provided by rigreference. The effect of Solar storms can be very peculiar.

• Sound Waves and Sources
• In General...
• Propagation of an Electromagnetic Wave
• Course Features
• continuous Wave: Whaler (Boston Whaler)

In some instances the storms will cause improved short-wave radio reception on the Earth. In other circumstances the storms will cause a complete blackout of short-wave radio reception.

In extreme conditions, the radiation from the Sun can actually cause damage to electrical systems orbiting the Earth e. Solar radiation, as well as affecting radio reception, also causes some of nature's wonders and in particular the Aurora Borealis and less well known Aurora Australis.

So now you know!When the wave enters the new medium, the speed of propagation will change. In order to match the incident and transmitted wave at the boundary, the transmitted wave will change its direction of . As a society we have become dependent on satellite communications, but satellites fail with alarming frequency.

Before the advent of satellites, long distance communications were carried out with high frequency (HF) radio transmissions. Wave propagation is the physics term for the movement of waves.

Electromagnetic waves don't need a material at all, and so they always travel at the same speed: 3 * 10^8 meters per second. Mar 11,  · A second version of this dataset combines the Wave Propagation model with the other Japan Tsunami datasets that are available here.

It starts by showing the earthquake activity leading up to the tsunami, then shows the tsunami wave propagation combined with earthquake activity and then ends with a map of maximum wave heights.

In solids, sound waves can propagate in four principle modes that are based on the way the particles oscillate. Sound can propagate as longitudinal waves, shear waves, surface waves, and in thin materials as plate waves.

Longitudinal and shear waves are the two modes of propagation most widely used in ultrasonic testing. This course discusses theoretical concepts and analysis of wave problems in science and engineering.

Examples are chosen from elasticity, acoustics, geophysics, hydrodynamics, blood flow, nondestructive evaluation, and other applications.