About Electromagnetic Pulse

Electromagnetic Pulse (EMP) is an instantaneous, intense energy field that can overload or disrupt at a

distance numerous electrical systems and high technology microcircuits, which are especially sensitive to power surges.  A large scale EMP effect can be produced by a single nuclear explosion detonated high in the atmosphere.  This method is referred to as High-Altitude EMP (HEMP).  A similar,smaller-scale EMP effect can be created using non-nuclear devices with powerful batteries or reactive chemicals.  This method is called High Power Microwave (HPM).  Several nations, including reported sponsors of terrorism, may currently have a capability to use EMP as a weapon for cyber warfare or cyber terrorism to disrupt communications and other parts of the U.S. critical infrastructure.  Also, some equipment and weapons used by the U.S. military may be vulnerable to the effects of EMP.

 The threat of an EMP attack against the United States is hard to assess, but some observers indicate that it is growing along with worldwide access to newer technologies and the proliferation of nuclear weapons.  In the past, the threat of mutually assured destruction provided a lasting deterrent against the exchange of multiple high-yield nuclear warheads.  However, now even a single, low-yield nuclear explosion high above the United States, or over a battlefield, can produce a large-scale EMP effect that could result in a widespread loss of electronics, but no direct fatalities, and may not necessarily evoke a large nuclear retaliatory strike by the U.S. military. This, coupled with published articles discussing the vulnerability of U.S. critical infrastructure control systems, and some U.S. military battlefield systems to the effects of EMP, may create a new incentive for other countries to rapidly develop or acquire a nuclear capability. Policy issues raised by this threat include (1) what is the United States doing to protect civilian critical infrastructure systems against the threat of EMP, (2) could the U.S. military be affected if an EMP attack is directed against the U.S. civilian infrastructure, (3) are other nations now encouraged by U.S. vulnerabilities to develop or acquire nuclear weapons, and (4) how likely are terrorist organizations to launch a smaller-scale EMP attack against the United States ?

There is more to the story than a list of questions. A way more interesting to learn EMP is online tutoring. with online math tutoring you’ll get math answers by submitting your math problems. some Precalculus help that we got from online tutoring is very useful. EMP has a lot of precalculations and we are sure about it. you can also get something like statistics help or even chemistry help. this is a fun and good way to learn EMP mathematics.

Basic Differences Between AM and FM

We need to mention a couple of other things before we leave the discussion of how radio works.  We’ve talked about AM and FM radio, but we haven’t explained the real difference.

In fact, there is a lot of difference — and not just a difference in the station numbers on your radio dial.

The first type of radio service — the one we’ve been talking about in the last couple of modules — was AM radio.

The term modulation refers to how sound is encoded on a radio wave called a carrier wave; or, more accurately, how the sound affects the carrier wave so that the original sound can later be detected by a radio receiver.

In the top-left of this drawing the RF energy (carrier wave) is not modulated by any sound.  There would be silence on your radio receiver.

Sound transmitted by an AM radio station affects the carrier wave by changing the amplitude (height) of the carrier wave, as shown on the left.

Unfortunately, this type of modulation is subject to static interference from such things as household appliances — and especially from lightening storms.

AM also limits the loud-to-soft range of sounds that can be reproduced (called dynamic range) and the high-to-low sound frequency range (called frequency response, to be explained below).

FM radio, which came along in the 1930s, uses a different approach than AM. It’s virtually immune to any type of external interference, it has a greater dynamic range, and it can handle sounds of higher and lower frequencies. This is why music, with its much greater frequency range than the human voice, sounds better on FM radio.

Note on the left that when the carrier wave of FM radio is modulated with sound that the distance between the waves, or the frequency of the carrier wave, changes.

Thus, AM radio works by changing the amplitude of the carrier wave and FM radio works by changing the frequency of the carrier wave.

Frequency Response

Frequency relates to the basic pitch of a sound — how high or low it is. A frequency of 20 Hz would sound like an extremely low-pitched note on a pipe organ — almost a rumble.

At the other end of the scale, 20,000 Hz would be the highest pitched sound that can be imagined, even higher than the highest note on a violin or piccolo.

As we’ve noted, frequency is measured in Hertz (Hz) or cycles per second (CPS). A person with exceptionally good hearing will be able to hear sounds from 20-20,000 Hz.

Since both ends of the 20-20,000Hz range represent rather extreme limits, the more common range used for FM radio and TV is from 50 to 15,000 Hz. (A typical AM radio signal does not cover this entire range.)

Although the 50-15,000 Hz doesn’t quite cover the full range that can be heard by people with good hearing, it covers almost all naturally occurring sounds.  Note in the drawing above that the ear does not hear all frequencies of sound at the same loudness, but a good microphone does.

The sound level or amplitude of sound in radio and TV stations is monitored and adjusted with the help of a volume units meter (VU meter) meter. One model is shown on the left.  Audio levels must be carefully controlled in broadcasting to keep noise and distortion from reducing the quality of sound.

How have radio and TV broadcasting been used in education?

Radio and television have been used widely as educational tools since the 1920s and the 1950s, respectively. There are three general approaches to the use of radio and TV broadcasting in education:

1. direct class teaching, where broadcast programming substitutes for teachers on a temporary basis;
2. school broadcasting, where broadcast programming provides complementary teaching and learning resources not otherwise available
3. general educational programming over community, national and international stations which provide general and informal educational opportunities

The most notable and best documented example of the direct class teaching approach is Interactive Radio Instruction (IRI).This consists of “ready-made 20-30 minute direct teaching and learning exercises to the classroom on a daily basis. The radio lessons, developed around specific learning objectives at particular levels of maths, science, health and languages in national curricula, are intended to improve the quality of classroom teaching and to act as a regular, structured aid to poorly trained classroom teachers in under-resourced schools.” IRI projects have been implemented in Latin America and Africa. In Asia, IRI was first implemented in Thailand in 1980; Indonesia, Pakistan, Bangladesh and Nepal rolled out their own IRI projects in the 1990s. What differentiates IRI from most other distance education programs is that its primary objective is to raise the quality of learning – and not merely to expand educational access – and it has had much success in both formal and non-formal settings. Extensive research around the world has shown that many IRI projects have had a positive impact on learning outcomes and on educational equity. And with its economies of scale, it has proven to be a cost-effective strategy relative to other interventions.

Mexico’s Telesecundaria is another notable example of direct class teaching, this time using broadcast television. The programme was launched in Mexico in 1968 as a cost-effective strategy for expanding lower secondary schooling in small and remote communities.Perraton describes the programme thus:

Centrally produced television programs are beamed via satellite throughout the country on a scheduled basis (8 am to 2 pm and 2 pm to 8 pm) to Telesecundaria schools, covering the same secondary curriculum as that offered in ordinary schools. Each hour focuses on a different subject area and typically follows the same routine – 15 minutes of television, then book-led and teacher-led activities. Students are exposed to a variety of teachers on television but have one home teacher at the school for all disciplines in each grade.

The design of the programme has undergone many changes through the years, shifting from a “talking heads” approach to more interactive and dynamic programming that “link[s] the community to the programme around the teaching method. The strategy meant combining community issues into the programs, offering children an integrated education, involving the community at large in the organization and management of the school and stimulating students to carry out community activities.” Assessments of Telesecundaria have been encouraging: drop out rates are slightly better than those of general secondary schools and significantly better than in technical schools. In Asia, the 44 radio and TV universities in China (including the China Central Radio and Television University), Universitas Terbuka in Indonesia, and Indira Ghandi National Open University have made extensive use of radio and television, both for direct class teaching and for school broadcasting, to reach more of their respective large populations. For these institutions, broadcasts are often accompanied by printed materials and audio cassettes.

Japan’s University of the Air was broadcasting 160 television and 160 radio courses in 2000. Each course consists of 15 45-minute lectures broadcast nationwide once a week for 15 weeks. Courses are aired over University-owned stations from 6 am to 12 noon. Students are also given supplemental print materials, face-to-face instruction, and online tutorials.

Often deployed with print materials, cassettes and CD-ROMS, school broadcasting, like direct class teaching, is geared to national curricula and developed for a range of subject areas. But unlike direct class instruction, school broadcasting is not intended to substitute for the teacher but merely as an enrichment of traditional classroom instruction. School broadcasting is more flexible than IRI since teachers decide how they will integrate the broadcast materials into their classes. Large broadcasting corporations that provide school broadcasts include the British Broadcasting Corporation Education Radio TV in the United Kingdom and the NHK Japanese Broadcasting Station. In developing countries, school broadcasts are often a result of a partnership between the Ministry of Education and the Ministry of Information.

General educational programming consists of a broad range of programme types – news programs, documentary programs, quiz shows, educational cartoons, etc. – that afford non-formal educational opportunities for all types of learners. In a sense, any radio or TV programming with informational and educational value can be considered under this type. Some notable examples that have a global reach are the United States-based television show Sesame Street, the all-information television channels National Geographic and Discovery, and the radio programme Voice of America.The Farm Radio Forum, which began in Canada in the 1940s and which has since served as a model for radio discussion programs worldwide, is another example of non-formal educational programming.