UV Light Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. Which type of UV rays usually do not reach the Earth?

1. Ultraviolet C (UVC)
2. Ultraviolet B (UVB)
3. Ultraviolet A (UVA)
4. None of the above

Ans. The correct answer is a. Ultraviolet C (UVC)

Explanation: Although UVC contains more energy than UVA and UVB, UVC radiation does not reach Earth due to the presence of O₂ and O₃ in the stratosphere. UVC light has enough energy to excite an electron in an oxygen molecule, causing it to move to a higher energy orbital in the same oxygen molecule. Almost all of the energy from UVC light is consumed.

Ques. What is the wavelength range for the UV spectrum of light?

1. 0.01 nm to 10 nm
2. 400 nm – 700 nm
3. 700 nm to 1 mm
4. 10 nm to 400 nm

Ans. The correct answer is d. 10 nm to 400 nm

Explanation: Ultraviolet (UV) radiation has a wavelength range of 10 nm to 400 nm, which is shorter than visible light but longer than X-rays. The visible region has a wavelength range of 380-750 nm while the X-ray region has a wavelength range of 0.01 to 10nm.

Ques. Are UV rays used to sterilize surgical equipment?

1. True
2. False

Ans. The correct answer is a. True

Explanation: In hospitals and other healthcare settings, medical UV sterilizers are an essential tool in protecting patients from infectious diseases. UV radiation is used in these devices to kill bacteria, viruses, and other microbes that might cause infections.

Ques. The source of ultraviolet light is

1. red hot iron ball
2. electric bulb
3. carbon arc-lamp
4. sodium vapor lamp

Ans. The correct answer is c. carbon arc-lamp

Explanation: The sun is the most effective source of UV radiation. UV lamps, arc welding, and mercury vapor lamps are examples of man-made ultraviolet sources. Some devices release UV radiation, such as carbon, xenon, and other arcs.

Ques. What is the ratio of the speed of infrared and ultraviolet rays in a vacuum?

1. 3 x 10⁸
2. 1.21
3. 1
4. 0

Ans. The correct answer is c. 1

Explanation: Since both infrared and ultraviolet rays are electromagnetic waves, they can travel with a speed of 3 x 10⁸ m/s in a vacuum. Hence the ratio of the speed of infrared and ultraviolet rays is equal to one in a vacuum.

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Short Answers Questions [2 Marks Questions]

Ques. What is UV light?

Ans. UV light (ultraviolet light) is a type of electromagnetic radiation with a wavelength of 10 to 400 nm, which is shorter than visible light but longer than X-rays. These are found in sunlight and contribute 10% of total solar light.

Ques. Define Ultraviolet-visible (UV-VIS) spectroscopy.

Ans. UV spectroscopy, also known as UV-visible spectrophotometry, refers to absorption or reflectance spectroscopy in the ultraviolet and neighboring visible parts of the electromagnetic spectrum.

Ques. Define visible light.

Ans. Visible light is the part of the electromagnetic spectrum that can be seen with the human eye. Visible light is required for eyesight. It shows a variety of frequencies and photon energies that enable humans to detect different colors.

Ques. Define electromagnetic radiation.

Ans. Electromagnetic waves are produced when an electric field comes into contact with a magnetic field. Electromagnetic waves are produced by the interaction of an oscillating magnetic field and electric fields. These waves are also thought to be the solutions to Maxwell's equation, one of the fundamental equations of electrodynamics.

Ques. What is the electromagnetic spectrum?

Ans. The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation, as well as the wavelengths and photon energies associated with it. The electromagnetic spectrum includes electromagnetic waves with frequencies ranging from less than one hertz to greater than 1025 hertz, corresponding to wavelengths ranging from thousands of kilometers to a fraction of the size of an atomic nucleus. 

Ques. What are the seven types of electromagnetic waves?

Ans. The seven types of electromagnetic waves are

• Radio waves
• Microwaves
• Infrared rays (IR rays)
• Visible light
• Ultraviolet rays (UV rays)
• X-rays
• Gamma rays

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Long Answers Questions [3 Marks Questions]

Ques. What are the different types of UV Light?

Ans. There are three types of UV light

• UVA (Ultraviolet-A): UVA light is one of two ultraviolet wavelengths with which the human body is regularly in contact within the atmosphere. Their wavelengths are longer than those of the other two categories. Because of their length, UVA rays penetrate deeper layers of skin.

• UVB (Ultraviolet-B): This radiation is known to have an effect on the human body through the atmosphere. Furthermore, the ozone layer absorbs a large portion of this radiation. It has a shorter wavelength and penetrates the skin more deeply.

• UVC (Ultraviolet-C): UVC rays, as well as some UVB wavelengths, are absorbed by the ozone layer. They have shorter wavelengths and are not known to cause harm since they cannot penetrate the earth's ozone layer.

Ques. What are the applications of UV Visible Spectroscopy?

Ans. The applications of UV visible spectroscopy are

• Dyes and colorants are characterized using UV-visible spectroscopy.
• It is used in medical laboratories for blood sugar and cholesterol tests.
• It is used to identify aromatic chemicals.
• It is also utilized for structural interpretation and the detection of organic molecule impurities.
• As a detector for High-Performance Liquid Chromatography (HPLC), a UV-visible spectrophotometer is used.

Ques. How do sunglasses protect the eyes from UV rays?

Ans. Sunglass lenses are constructed of glass, plastic, or polycarbonate and have a specific UV-absorbing coating. 

• An adequate pair of sunglasses can prevent 99% of UV rays from reaching the human eye. 
• Tints and mirror coatings prevent squinting by absorbing or reflecting strong, bright light in the visible spectrum. 
• The high-quality sunglasses have a polarising coating to reduce glare from horizontal surfaces such as water, sand, and snow.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the applications of UV rays?

Ans. The following are the applications of UV rays

• UV rays are used in tanning booths to expose our bodies to UV radiation, which causes our bodies to produce melanin, which darkens our skin. Tanning booths tan the skin by using artificial UV radiation in lamps.
• To photograph fingerprints, UV radiation, often known as black light, is used. UV rays can be used as a spray or immersion to detect fingerprints with the help of fluorescent powders or solutions. 
• UV rays are used to analyze the chemical structure of a molecule by changing its color. A spectrophotometer is a machine that analyses the chemical structure of a material by measuring the change in color. This can be found in water laboratories, biological facilities, and the petrochemical industry.
• Polyphenols, a plant that is considered to be helpful in the prevention of cancer, are produced by the influence of UV radiation. Psoralens, a medication that responds to UVA ultraviolet therapy, is given to patients.
• To identify fake currency notes, UV rays are used. UV radiations are used to expose currency notes, and the radiations are used to verify that the UV markings are authentic.

Ques. What are the harmful health effects of UV radiation?

Ans. The harmful health effects of UV radiation are

• Excessive exposure to UV radiation can cause severe sunburns, wrinkles, and premature skin aging, as well as an increase in the risk of skin cancer and cataracts. 
• Excessive sun exposure may be responsible for around 80% of all skin cancer incidences. 
• According to research, UVB produces tanning of our skin slowly but considerably boosts the development of skin cancer, whereas UVA causes wrinkling, aging, and quick tanning effects and may also promote the development of skin cancer. 
• The World Health Organisation believes that up to 20% of cataracts may be caused by UV overexposure. 
• As a result, one should not underestimate the possible harm that UV overexposure may cause.

Ques. How ozone layer help us from harmful ultraviolet radiations?

Ans. The ozone layer is a region of high ozone concentration in the stratosphere, located between 15 and 35 kilometers above the Earth's surface. The ozone layer works as an invisible screen, shielding humans from the sun's damaging ultraviolet (UV) rays.

• The ozone layer shields humans from UV-B light, which causes sunburn. Long-term UV-B exposure harms human health and damages most animals, plants, and microorganisms, hence the ozone layer protects all life on Earth.

• UV-B rays from the sun are absorbed by ozone. When an ozone molecule absorbs UV-B, it splits into an oxygen molecule and a single oxygen atom. The two components can later rebuild the ozone molecule. The ozone layer prevents harmful levels of UV-B radiation from reaching the Earth's surface by absorbing it in the stratosphere.

• In addition to UV-B, the sun emits UV-C ultraviolet radiation. UV-C radiation is entirely absorbed by oxygen molecules in the stratosphere and never reaches the Earth's surface. UV-C breaks oxygen molecules into oxygen atoms. These isolated oxygen atoms then combine with other oxygen molecules to form ozone. As a result of these processes, the amount of ozone in the stratosphere increases.

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