Infrared Radiation Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. Who found infrared radiation?

1. Sir William Herschel
2. Newton
3. Kepler
4. Michel Faraday

Ans. The correct answer is a. Sir William Herschel

Explanation: Infrared radiation was discovered by the astronomer Sir William Herschel in 1800.

Ques. Infrared radiation is a type of electromagnetic radiation that has:

1. Longer wavelengths than visible light
2. Shorter wavelengths than visible light
3. The same wavelengths as visible light
4. No wavelengths

Ans. The correct answer is a. Longer wavelengths than visible light

Explanation: Infrared radiation has longer wavelengths than visible light. Visible light has wavelengths that range from 380 nanometers (nm) to 750 nm, while infrared radiation has wavelengths that range from 700 nm to 1 millimeter (mm).

Ques. In what form is solar energy radiated from the sun?

1. Electromagnetic waves
2. Ultraviolet Radiation
3. Infrared radiation
4. Transverse waves

Ans. The correct answer is a. Electromagnetic waves

Explanation: The sun emits solar energy in the form of electromagnetic waves with shorter wavelengths ranging from 0.2 to 0.4 micrometers. Out of all the solar energy radiations that reach the earth's atmosphere, 8% are ultraviolet radiation, 40% are visible light, and 46% are infrared radiation.

Ques. Solar radiation that reaches the surface without scattering or absorbed is called

1. Infrared radiation
2. Diffuse radiation
3. Ultraviolet radiation
4. Beam Radiation

Ans. The correct answer is d. Beam radiation

Explanation: Direct radiation or beam radiation is solar energy that has not been absorbed or scattered and reaches the ground directly from the sun. When the radiation is interrupted by an opaque object, it produces a shadow.

Ques. Which of the following materials is transparent to infrared radiation?

1. Metal
2. Wood
3. Paper
4. Glass

Ans. The correct answer is d. Glass

Explanation: Glass is transparent to infrared radiation, which means that it allows infrared light to pass through it. This is why glass is used in greenhouses to trap heat from the sun.

Ques. Which of the following is the main source of infrared radiation on Earth?

1. Moon
2. Sun
3. Artificial light sources
4. Stars

Ans. The correct answer is b. Sun

Explanation: The Sun is the main source of infrared radiation on Earth. From near-infrared to far-infrared, the Sun emits infrared light at all wavelengths.

Ques. Infrared radiation has a heat-inducing property.

1. Yes
2. No

Ans. The correct is a. Yes

Explanation: Because infrared radiations produce heat, they are used for medicinal purposes or in infrared heaters.

Ques. Which among the following is used in astronomical telescopes and optical fiber communications?

1. Near-infrared
2. Long-wavelength infrared
3. Medium infrared
4. Far infrared

Ans. The correct answer is b. Long-wavelength infrared

Explanation: Astronomical telescopes and optical fiber communications depend on long-wavelength infrared.

Ques. The branch of science that studies the interactions of electromagnetic waves with matter is

1. Bioscopy
2. Archaeology
3. Spectroscopy
4. Paleontology

Ans. The correct answer is c. Spectroscopy

Explanation: Spectroscopy is the study of the spectrum of electromagnetic radiation emitted or absorbed by matter.

Ques. Which type of infrared radiation is used in TV remote sensors?

1. Far-infrared rays
2. Near-infrared rays

Ans. The correct answer is b. Near-infrared rays

Explanation: Near-infrared radiation is used in TV remote sensors because it is cheap and easy to produce with infrared LEDs.

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Short Answers Questions [2 Marks Questions]

Ques. What is infrared radiation?

Ans. Infrared radiation (IR) is electromagnetic radiation that occurs in the spectral range between radio waves and visible light. It is not visible to the human eye.

Ques. What is the wavelength of the infrared radiation?

Ans. The wavelength of infrared radiation ranges from 780 nanometers (nm) to 1 millimeter (mm). This is longer than the wavelengths of visible light, which range from 380 nm to 780 nm.

Ques. What is the electromagnetic spectrum?

Ans. The entire distribution of electromagnetic radiation according to frequency or wavelength is referred to as the electromagnetic spectrum. The electromagnetic spectrum includes all electromagnetic radiation and is divided into various subranges, known as parts, such as visible light or ultraviolet radiation.

Ques. How infrared radiations are produced?

Ans. Infrared waves are produced by hot bodies and molecules because of their thermal motion. When a body or molecule is hot, its atoms and molecules vibrate more rapidly. This vibration causes the atoms and molecules to emit electromagnetic radiation in the infrared spectrum.

Ques. Why are infrared waves often called heat waves?

Ans. Infrared waves are also called heat waves because when a body comes in contact with infrared waves, it causes the atoms and molecules to vibrate. Due to these vibrations, the internal energy and hence temperature of the body increases.

Ques. Which instrument is used to detect infrared radiation?

Ans. Pyrometers are remote-sensing thermometers that are sensitive to infrared radiation, so they can be used to detect infrared radiation.

Ques. What are the three types of infrared radiation?

Ans. The three types of infrared radiation are

• Near-infrared radiation (NIR)
• Mid-infrared radiation (MIR)
• Far-infrared radiation (FIR)

Ques. What are the different sources of infrared radiation?

Ans. Solar radiation and fire are the common natural sources of infrared radiation. Heating devices and infrared lamps are used in the home and in infrared saunas for health purposes are the common sources of artificial infrared radiation.

Ques. What is the infrared spectroscopy?

Ans. Infrared spectroscopy is the study of how infrared light interacts with materials through absorption, emission, or reflection. It is used for studying and determining chemical compounds or functional groups in their solid, liquid, or gaseous states.

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Long Answers Questions [3 Marks Questions]

Ques. How to select infrared detectors?

Ans. The criteria for selecting infrared detectors are as follows:

• The temperature and wavelength of an object must be measured.
• It is important to consider photosensitivity and signal-to-noise ratio. 
• In order to reduce signal noise, the infrared detector must be cooled using either thermoelectric, mechanical, or cryogenic cooling.
• Depending on the use of the infrared detector, response speed, and chopping frequency must be recorded.
• When using infrared detectors in optical systems, the active area's size and shape are essential.
• Infrared detectors are available in a variety of packaging, including metal cans and ceramic packages.

Ques. What is the classification of the infrared detector?

Ans. The following are the classifications of the infrared detectors

• Thermal type: Heat is supplied to thermal type detectors by infrared radiation, and photosensitivity is wavelength-independent. The thermocouple is an example of a thermal infrared detector.
• Quantum type: This can be an intrinsic or extrinsic form. The detecting performance is superior to that of the thermal type. Intrinsic type is further separated into two categories: photoconductive and photovoltaic type. The photosensitivity of these detectors depends on the wavelength.

Ques. List a few medicinal effects of infrared radiation.

Ans. Some medical effects of infrared radiation are as follows:

• Used to relieve inflammation in the throat, ears, and nose.
• Used to help control stress.
• Reduces pain from arthritis
• It improves the functioning of the kidneys.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the applications of infrared radiation?

Ans. The following are the applications of infrared radiation

• Astronomy: Astronomers analyze space objects using infrared wavelengths using optical instruments such as digital detectors, mirrors, and lenses. Images of these devices can be obtained using an infrared telescope.
• Heat source: This radiation is used as a heat source in the medical and manufacturing industries. Infrared saunas can be used to treat rheumatoid arthritis, high blood pressure, and other chronic health conditions. It's also a risk-free type of physical treatment. Infrared heaters are used in the production unit for coating curing, plastic forming, and plastic welding.
• Infrared photography: Images can be captured using infrared filters. The imaging is done for objects that are in the near-infrared spectrum.
• Cosmetology: This radiation is used to treat dandruff, skin injuries, blackheads, and wrinkles. They also increase the delivery of oxygen, blood circulation, and nutrition supply to the skin.
• Massage therapy: Infrared rays are used to warm the skin and relax the muscles. Infrared rays are preferred for skin penetration because they can penetrate the skin more deeply.

Ques. What are the characteristics of infrared radiation?

Ans. The following are the characteristics of infrared radiation:

• Transverse wave: Infrared waves are transverse waves, which means that their displacement is at a right angle to the direction of wave propagation.
• Wavelength: Infrared rays have different wavelengths that are commonly measured in microns. The shortest wavelength of an infrared wave is about 0.7 microns. The longest wavelength of an infrared wave is 350 microns.
• Speed: The speed of the infrared radiation is equal to the speed of the light i.e. 3 x 108 m/s.
• Absorption and Reflection: The nature of the substance that infrared rays impact determines their absorption and reflection. Infrared radiation is absorbed by materials such as ozone, carbon dioxide, and water vapor. Infrared radiation is reflected by snow and aluminum foil.
• Refraction and Interference: Infrared waves have the property of refraction, which causes a small shift in direction when they move from one medium to another. Infrared wave refraction may be observed in the Earth's atmosphere. When two infrared waves of the same wavelength combine, they interfere with one another.
• Thermal Properties: Because infrared radiation has thermal characteristics, it can be used as a source of heat. When infrared light strikes oxygen or nitrogen molecules, the molecules accelerate as they gather energy. As a result, infrared radiation heats objects and can be used as a heat source.

Ques. What are the characteristics of the region of the infrared radiation?

Ans. Infrared radiation is classified into many regions. The following table describes the characteristics of the regions:

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