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Radio waves can be expressed as the waves that have the longest wavelength in the electromagnetic spectrum. Radio waves are a type of electromagnetic radiation well-known for their use in communication technologies, such as television, cellphones, and radios. These devices detect radio waves and convert them into mechanical motion on the speaker to create sound waves. The radio spectrum is the smallest part of the electromagnetic (EM) spectrum.
| Table of Content |
Key Terms: Electromagnetic Waves, Radio Waves, Wavelengths, Frequency, Electromagnetic Spectrum, Wave Propagation, Bands
What are Electromagnetic Waves?
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Electromagnetic waves are those which are a sinusoidal variation of electrical vectors and magnetic forces at right angles to each other and right angles in the direction of wave propagation.
The range and categorization of all these types of electromagnetic waves according to their frequency are known as the “electromagnetic spectrum.” Electromagnetic spectrum can also be defined as the distribution of electromagnetic waves, depending on their length and frequency.
Rapid charges emit electric waves. An oscillating charge is an example of speeding up of charge. Electromagnetic waves are also produced when rapidly moving electrons are stopped by a metallic surface of a high atomic number.
Electric waves without light also have the same speed c in the free space.
The speed c of electrical waves in a vacuum is related to μ0 and ε0 are as follows:
Electric waves without light also have the same speed c in the free space. The speed of light or electric waves in the medium is given by:
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| Concept Related Links | ||
|---|---|---|
| Progressive Wave | Intensity Formula | Electromagnetic Pulse |
| Remote Sensing | Bandwidth of a Signal | Period Angular Frequency |
| Space Wave Propagation | X-rays | Ground Wave Propagation |
Types of Electromagnetic Waves
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Electromagnetic waves usually possess both magnetic as well as electric fields. They are further based on their frequency. The different types of electromagnetic waves in the electromagnetic spectrum are tabulated below:
| Type of Radiation | Frequency Range in Hz | Wavelength Range | Uses |
|---|---|---|---|
| Gamma-rays | 1020 – 1024 | < 10-12 m | Sterilize medical equipment, Medical Treatment, and Treatment of cancer (without surgery) |
| X-rays | 1017 – 1020 | 1 nm – 1 pm | Treat tumors, Detect brain fractures or sprains |
| Ultraviolet | 1015 – 1017 | 400 nm – 1 nm | Disinfection, Sterilization without the use of chemicals |
| Visible | 4 – 7.5 x1014 | 750 nm – 400 nm | For performing scientific experiments and LEDs |
| Infrared | 1013 – 1014 | 25 μm – 2.5 μm | Study human body heat patterns, used in infrared cameras |
| Microwaves | 3 x1011 – 1013 | 1 mm – 25 μm | Used for cooking in microwaves |
| Radio waves | < 3 x 1011 | > 1 mm | Used in the operation of radio through catching frequencies |
What are Radio Waves?
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Radio waves are produced by the rapid movement of charges in conducting wires. These waves have low power levels and low frequencies ranging from about 3 kHz to about 300 GHz. Mostly, the radio waves have a frequency range from 500 kHz to about 1000 MHz.
Radio waves have the longest wavelengths in the electromagnetic spectrum, according to NASA, from about 0.04 inches (1 millimeter) to over 100 miles (100 km). Also, they have very low frequencies, ranging from about 3,000 cycles per second, or 3 kilohertz, to 300 million hertz, or 300 gigahertz. The NTIA (National Telecommunications and Information Administration) have divided the radio waves into 9 bands, which are given in the table below:
| Band | Frequency Range | Wavelength Range |
|---|---|---|
| Extremely low frequency (ELF) | <3 kHz | > 100 km |
| Very low frequency (VLF) | 3 to 30 kHz | 10 to 100 km |
| Low Frequency (LF) | 30 to 300 kHz | 1 m to 10 km |
| Medium Frequency (MF) | 300 kHz to 3 MHz | 100 m to 1 km |
| High frequency (HF) | 3 to 30 Mhz | 10 to 100 m |
| Very high frequency (VHF) | 30 to 300 MHz | 1 to 10 m |
| Ultra-high frequency (UHF) | 300 MHz to 3 GHz | 10 cm to 1 m |
| Super high frequency (SHF) | 3 GHz to 30 GHz | 1 to 1 cm |
| Extremely high frequency (EHF) | 30 GHz to 300 GHz | 1 mm to 1 cm |
Uses of Radio Waves
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Radio waves are used in almost all electronic communication devices. Some of the uses of Radio Waves include:
- Radio waves are used in radio communications, radar, computer systems, broadcasts, multi-channel frames, and many more.
- It is used in the radio and television communication setup.
- They are also used for mobile and Wifi/LAN communications.
- Radio waves are often used in remote-controlled toys.
- It is used in the navigation process from space to the ground.
- It is used for air-trafficking control.
- Radio waves and microwaves are used in television, wireless radio, and cellular communication.
Previous Year Questions
- A 100Ω resistance and a capacitor of 100Ω reactance … [NEET 2016]
- The electric field part of an electromagnetic wave in a medium … [NEET 2009]
- The electric and magnetic field of an electromagnetic wave … [NEET 1994]
- In which of the following, emission of electrons … [NEET 1990]
- If λv,λx,λm represent the wavelengths of visible light … [NEET 2005]
- A parallel plate capacitor of capacitance … [NEET 2019]
- A radiation of energy 'E' falls normally on a perfectly … [NEET 2015]
- An electromagnetic wave of frequency … [NEET 2013]
- Biological importance of ozone layer … [NEET 2001]
- If ε0 and μ0 are the electric permittivity … [NEET 1997]
- Light with an energy flux of … [NEET 2014]
- The condition under which a microwave oven heats up … [NEET 2013]
- The electric field associated with an … [NEET 2012]
- The ratio of contributions made by the electric field … [NEET 2020]
- The velocity of electromagnetic wave is parallel … [NEET 2002]
- Sky wave propagation is …. (VITEEE 2011)
- The frequency of an FM transmitter …. (VITEEE 2011)
- The attenuation in optical fibre is mainly due to…. (VITEEE 2010)
- Sinusoidal carrier voltage of frequency 1.5MHz …. (VITEEE 2010)
- In amplitude modulation, the amplitude of … (VITEEE 2019)
- Amplitude modulation … (KCET 2015)
Things to Remember
- Radio waves are produced by the rapid movement of charges.
- These waves have low power levels and low frequencies ranging from about 3 kHz to about 300 GHz.
- Radio waves have 9 bands depending on the frequencies.
- Radio waves are used in radio communications, radar, computer systems, broadcasts, multi-channel frames, and many more.
- Radio waves have the longest wavelengths in the electromagnetic spectrum.
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Sample Questions
Ques. What is the speed of the radio waves? (2 marks)
Ans. In a vacuum, the speed of radio waves is much faster, ‘the speed of light.’ The movement of radio waves depends on what they are traveling on, the extreme in space, the slow movement of objects depends on the type of element and the frequency of the waves.
Ques. How are radio waves created? (2 marks)
Ans. Radio waves are created artificially by the transmitters and caught by radio collectors. It is produced by the accelerating movement of charges in conducting wires.
Ques. What are FM radio waves? (2 marks)
Ans. FM radio waves are a type of radio wave that carries signals ranging from 88 to 108 kHz.
Ques. What are AM radio waves? (2 marks)
Ans. AM radio waves are a type of radio wave that carries radio signals ranging between 540 to 1600 kHz.
Ques. Why is the radio waves unit considered Hertz? (2 marks)
Ans. Heinrich Hertz showed radio waves in his laboratory in 1887. Hertz is a radio measurement unit, named after Heinrich Hertz.
Ques. Define Electromagnetic Spectrum. (2 marks)
Ans. The systematic sequential distribution of electromagnetic waves in ascending or descending order of frequency or wavelength is known as electromagnetic spectrum. The range varies from 10-12 m, to 104 m, i.e. from γ-rays to radio waves.
Ques. Mention some of the uses of electromagnetic waves (3 marks)
Ans. Radio waves
(i) In radio and TV communication.
(ii) In the astronomical field.
Microwaves
(i) In RADAR communication.
(ii) In analysis of molecular and atomic structure.
(iii) For cooking purposes.
Infrared waves
(i) In knowing molecular structure.
(ii) In remote control of TV VCR, etc.
Ultraviolet rays
(i) Used in burglar alarms.
(ii) To kill germs in minerals.
X-rays
(i) In medical diagnosis as they pass through the muscles not through the bones.
(ii) In detecting faults, cracks, etc.,in metal products.
γ-rays
(i) As food preservation.
(ii) In radiotherapy.
Ques. Write the following radiations in ascending order in respect of their frequencies ;
X-rays, Microwaves, UV rays and radio waves. (Delhi 2009) (1 mark)
Ques. Mention some of the uses of Radio waves. (2 marks)
- They are also used for mobile and Wifi/LAN communications.
- Radio waves are often used in remote-controlled toys.
- It is used in the navigation process from space to the ground.
- It is used for air-trafficking control.
- Radio waves and microwaves are used in television, wireless radio, and cellular communication.
Ques. Which wave has the shortest wavelength? (1 mark)
Ans. X-rays have the shortest wavelength and the highest frequency.
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