The differences between Infrared Radiations vs Microwaves vs Radio Waves, their wavelength, frequency ranges, properties, applications, and real-world uses are discussed here.
Table of Contents
Introduction
The electromagnetic spectrum (EM) is a continuous continuum of electromagnetic waves (EMW). It ranges from extremely long wavelengths (low frequencies) to extremely short wavelengths (high frequencies).
Unlike mechanical waves that require a medium to flow (such as sound waves), electromagnetic waves do not require a material medium and can propagate through a vacuum.
For ease of study, the spectrum can be divided into three regions (though this is not a strict or primary rule):
- The infra-region comprises lower-frequency waves such as infrared radiation (IR), microwaves (MW), and radio waves (RW).
- The visible region, a narrow band in which human eyes perceive light (roughly between 430 THz and ~770 THz).
- The ultra-region, containing higher-frequency radiation (ultraviolet, X-rays, gamma rays, etc.).
Note that infra-region and ultra-region are not standard literature or textbook terms. These are just meant to make things easier to grasp and understandable.
3 Fundamental Properties of Electromagnetic Waves
Before delving into the infra-region of EM waves, it is essential to recall 3 key relations that govern all electromagnetic radiation:
a. Wave–Speed Relation
Where,
= speed of light in vacuum (~
= wavelength
= frequency
= speed of light in vacuum (~
= wavelength
= frequencyb. Photon Energy
Where,
- = Planck’s constant (~
) - = frequency
= energy
= Planck’s constant (~
)
= energyThis relation shows that higher-frequency waves carry more energy per photon.
c. Continuity and Boundaries
The electromagnetic spectrum is continuous, and the “boundaries are not sharply defined” between infrared and visible, or between microwave and radio. Boundaries are conventional and context-dependent. These equations and principles apply equally to all parts of the electromagnetic spectrum, including.
Infra-Region of the EM spectrum
The infra-region is the segment of the electromagnetic spectrum with lower frequencies than visible light. Although precise numerical limits differ slightly in the literature, a common approximation is:
- Lower bound (infrared end): frequency around 430 THz (wavelength about 700 nm)
- Upper bound (radio end): frequency around 3 kHz (wavelength about 1000 km)
Between these extremes, the infra-region is often subdivided into:
- infrared radiation (IR)
- microwaves (MW)
- radio waves (RW)
Each sub-region overlaps slightly with its neighbours. In practice, the divisions are functional (based on applications and interactions with matter) rather than sharply defined.
Here, you will exclusively learn about the infra-region, which is inhabited by:
Although invisible to the human eye, these waves are indispensable across many realms of science, engineering, and daily life.
1. Infrared Radiation
Range: 700 nanometres (nm) – 1 millimetre (mm)
Frequency: 430 THz – 300 GHz
Characteristics
Infrared radiation lies immediately beyond the red end of visible light. Although invisible, it is most strongly experienced as heat radiation.
Everyday objects at room temperature emit infrared continuously. For example, the human body radiates IR due to its average surface temperature of ~37°C.
Molecular Interactions
Infrared photons are strong enough to excite molecular vibrations; however, not powerful enough to cause electronic transitions. This property makes IR particularly useful in spectroscopy. This technique allows scientists to identify substances based on their vibrational “fingerprints”.
Applications
- Astronomy (space telescopes such as James Webb explore dust-obscured regions in IR)
- Thermal Imaging (security, firefighting, medical diagnosis)
- Remote Controls (televisions, projectors, air conditioners)
- Medical Diagnostics (detection of fevers, inflammation)
2. Microwaves
Range: 1 millimetre (mm) – 1 meter (m)
Frequency: 300 GHz – 300 MHz
Characteristics
Microwaves occupy the spectral region between infrared and radio waves. They are especially notable for their ability to penetrate the atmosphere of the Earth and to interact strongly with polar molecules such as water.
Because most microwave frequencies experience minimal atmospheric absorption, they are widely used in long-distance communication technologies and domestic use.
Physical Interactions
Water molecules resonate at microwave frequencies, absorbing energy and converting it into heat. This is the principle behind microwave ovens, where food is heated by the agitation of water molecules.
Applications
- Microwave Ovens (food heating and cooking)
- Communication Technologies (Wi-Fi, Bluetooth, satellite links)
- Radar Systems (navigation, weather monitoring, military defence)
- Cosmology (detection of the Cosmic Microwave Background, the afterglow of the Big Bang)
3. Radio Waves
Range: 1 m – 1000 km
Frequency: 300 MHz – 3 kHz
Characteristics
Radio waves are the longest-wavelength members of the electromagnetic spectrum. They are the leader of global communication due to their ability to travel great distances and reflect off the ionosphere.
Sources of Radio Waves
As of today, there are two known sources of radio waves, namely:
- Natural: lightning, pulsars, quasars, galaxies
- Artificial: broadcasting stations, cellular towers, navigation systems
Applications
- Radio and television broadcasting
- Global Positioning System (GPS)
- Cellular and wireless communication
- Radio astronomy enables scientists to study black holes, galaxies, and the cosmic structure.
Why Focus on the Infra-region?
Although invisible, the infra-region is arguably the most practically important portion of the electromagnetic spectrum for daily life and much of modern technology. Within it, one finds:
- Remote sensing and thermal imaging (infrared)
- Wireless communication, radar, satellite links (microwaves)
- Broadcasting, navigation, and long-distance transmission (radio waves)
Furthermore, the infra-region is deeply linked to the physical processes of heat, molecular vibration, and long-distance electromagnetic propagation in media (including free space, ionosphere, and atmosphere).
By concentrating on the infra-region, we can explore how invisible waves power much of modern science and infrastructure.
The Infra-region at a Glance
| Property | Infrared | Microwaves | Radio Waves |
| Wavelength Range | 700 nm – 1 mm | 1 mm – 1 m | 1 m – 100+ km |
| Frequency Range | 430 THz – 300 GHz | 300 GHz – 300 MHz | < 300 MHz |
| Key Applications | Heat sensing, spectroscopy, astronomy, and medical imaging | Cooking, Wi-Fi, radar, satellites, cosmology | Broadcasting, GPS, radio astronomy |
| Notable Fact | Pit vipers and some snakes detect infrared to “see” warm-blooded prey at night. | Microwaves are the same type of radiation your phone uses to connect to the internet. | Wolves, lions, and other animals are tracked using radio collars. |
Conclusion
The infra-region of the electromagnetic spectrum includes infrared radiation, microwaves, and radio waves. These are all invisible to the naked eye, yet indispensable to human civilisation.
- Infrared radiation reveals heat and molecular vibrations and has its uses in medicine, security, and astronomy.
- Microwaves drive both daily conveniences (cooking, Wi-Fi) and large-scale systems (radar, satellites, cosmology).
- Radio waves enable broadcasting, navigation, wireless communication, and deep-space exploration.
Together, these waves demonstrate that while human eyes perceive only a sliver of the spectrum. The unseen infra-region forms the backbone of both modern technology and scientific discovery.
Frequently Asked Questions (FAQs)
Write the differences between Infrared Radiations vs Microwaves vs Radio Waves.
| Property | Infrared Radiation | Microwaves | Radio Waves |
| Wavelength | 700 nm – 1 mm | 1 mm – 1 m | 1 m – 1000 km |
| Frequency | 430 THz – 300 GHz | 300 GHz – 300 MHz | 300 MHz – 3 kHz |
| Characteristics | Experienced as heat; excites molecular vibrations | Penetrates atmosphere; interacts with water molecules | Longest waves travel long distances and reflect off the ionosphere |
| Applications | Thermal imaging, spectroscopy, and remote controls | Microwave ovens, Wi-Fi, radar, satellites | Radio & TV broadcasting, GPS, cellular communication |
| Notable Fact | Snakes detect IR to sense warm-blooded prey | The same type of radiation is used in mobile phones | Radio collars track animals like wolves and lions |
Two types of Electromagnetic radiation are used in glass optical fibers for high-speed broadband. State the type of Electromagnetic radiation, other than visible light, which is used in glass optical fibers.
Infrared with a wavelength of 850–1550 nm is the closest EM radiation (other than visible light) that can be used because in glass fibres as it suffers minimal attenuation.
Give two reasons why Visible Light and Infrared radiation are used in glass optical fibers for high-speed broadband.
- Longer Distance Travelled
- High Data Transmission Rates
These EM radiations can travel long distances with minimal attenuation in optical fibres. They also allow high data transmission rates due to their short wavelengths compared with MW and RW.
Visible light has a frequency of approximately 5.0× 1014 Hz. M and N are two other types of Electromagnetic radiation.
i. The frequency of M is 5.0× 106 Hz.
ii. The frequency of N is 5.0× 1015 Hz.
Which type of radiation are M and N?
- M:
Hz → Radio - N:
Hz → Near-UV
Hz → Radio
Hz → Near-UVRadiations from which part of the electromagnetic spectrum are used in a remote controller for a television? Also, which Part of the electromagnetic spectrum is used to send television signals from a satellite to Earth?
- Remote controller → Infrared (IR), typically
- Satellite TV signals → MW, typically
A transmitter produces radio waves of wavelength 1500m. It takes the waves 0.025s to travel from the transmitter to a radio receiver. What is the distance between the radio transmitter and the receiver?
Distance = Speed × Time
An intruder alarm sensor detects that a person is warmer than his surroundings. Which type of electromagnetic wave does the sensor detect? Which part of the electromagnetic spectrum is used by a remote controller for a television?
Infrared (IR) in both cases.
Reason
Warm objects emit IR due to thermal radiation, and IR LEDs are used in remotes to transmit coded signals.
A radio transmitter broadcasts at a frequency of 200 kHz. What is the wavelength of these radio waves?
Speed = Frequency × Wavelength
The sun emits infrared radiation and light. Light from the sun reaches the Earth in 8 minutes. Which information about the infrared radiation is correct?
i. Wavelength of infrared radiation
ii. Time taken for infrared radiation to reach the Earth
- Wavelength range of infrared radiation: ~700 nm – 1 mm
- Time taken to reach the Earth: ~8 minutes (same as visible light, because IR travels at the speed of light)
What is the speed of microwaves in air?
MW travel with an astonishing speed of ~
(same as light).
The frequency of the microwaves used in a microwave oven is 2400 MHz. What is the wavelength of these microwaves?
Speed = Frequency × Wavelength
