EM-Waves-Presentation (1)

Definition: Radio waves have the longest wavelength in the electromagnetic spectrum.
Production: Produced by making electrons vibrate in an antenna.
Uses: Transmit sound and picture information over long distances.

Radio waves have a wide range of wavelengths divided into smaller regions known as wavebands.
Each waveband is allocated by law to a specific radio service.
Table 2: Radio Waves Frequencies:
- Extremely Low Frequency (ELF): < 3 kHz, > 100 km
- Very Low Frequency (VLF): 3-30 Hz, 10-100 km
- Low Frequency (LF): 30-300 kHz, 1-10 km (Radio communication)
- Medium Frequency (MF): 300 kHz - 3 MHz, 100 m - 1 km (AM radio broadcasting)
- High Frequency (HF): 3 - 30 MHz, 10 - 100 m (AM radio broadcasting)
- Very High Frequency (VHF): 30 - 300 MHz, 1 - 10 m (FM radio broadcasting, TV Broadcasting)
- Ultra High Frequency (UHF): 300 MHz - 3 GHz, 10 cm - 1 m (FM radio broadcasting, TV Broadcasting)
- Super High Frequency (SHF): 3 - 30 GHz, 1 - 10 cm (Satellite Communication)
- Extremely High Frequency (EHF): 30 - 300 GHz, 1 mm - 1 cm

Low frequency waves are suitable for long-distance communication but limited by the earth's curvature (approx. 80 km).
Repeaters are used to extend the range by receiving and re-transmitting signals.
High frequency waves can be reflected by the ionosphere, allowing transmission over vast distances.

Medium and high frequency waves are utilized for local radio station broadcasting.
Audio signals, converted via a microphone, produce audio-frequency (AF) signals.
Amplitude Modulation (AM): Amplitude of the RF carrier changes to match the AF signal, effective for long-distance broadcasting.
Frequency Modulation (FM): Frequency of RF waves changes to match the AF signal, providing higher quality broadcasting including stereo sound.

Definition: Microwaves have shorter wavelengths than radio waves.
Applications: Used in satellite communications, radar, television transmission, and cooking.
- Satellite Communications: Microwaves penetrate the earth's atmosphere, enabling satellite interactions. Communication satellites orbit at 35,000 km altitude, appearing stationary.

Radar systems consist of an antenna, transmitter, and receiver.
The antenna continuously scans the area, sending narrow pulses of microwaves that reflect off objects.
The distance to an object is calculated based on the time delay between sending and receiving pulses.

Definition: Lies beyond the red end of the visible light spectrum, emitted by all objects depending on temperature.
Applications include:
1. Infrared photography for vegetation imaging from satellites.
2. Medical diagnostics through body temperature variations.
3. Remote controls for electronic devices.

Sources: Primarily from the sun, with artificial sources available.
Applications:
- Checking signatures on passbooks with UV lamps.
- Sterilizing water and identifying fake banknotes.
- Stimulating Vitamin D production in skin, but overexposure can lead to skin cancer.

Composition: When white light passes through a prism, it separates into red, orange, yellow, green, blue, indigo, and violet.
The eye is sensitive to electromagnetic waves of wavelengths ranging from 400 to 700 nm.
Table 3: Wavelengths of Colors in White Light:
- Violet - Indigo: 390 to 455 nm
- Blue: 455 to 492 nm
- Green: 492 to 577 nm
- Yellow: 577 to 597 nm
- Orange: 597 to 622 nm
- Red: 622 to 700 nm

Definition: Fell just after ultraviolet rays with shorter wavelengths and higher energy.
Production: Emitted when fast-moving electrons hit a metal target.
Uses: Medical imaging for diagnosing fractures and tumors; can penetrate metals to inspect welds.
Caution: Frequent exposure is dangerous, increasing cancer risk.

Definition: Shortest wavelength, high frequency, and energy in the electromagnetic spectrum.
Sources: Emitted by stars and some radioactive materials.
Uses: Employed in cancer treatment (radiotherapy) and sterilization of drinking water, but can be lethal to living cells. Only blocked by lead and thick concrete.