[Physics Class Notes] on Ultraviolet Rays Pdf for Exam

Have you ever wondered by looking up at the sky and thinking about what causes the deep blue color? You may not realize but electromagnetic waves play a major role in this. 

 

The electromagnetic spectrum is the combination of radio waves, microwaves, infrared waves, visible light, UV light, and also X-rays and gamma rays. The interesting thing is, electromagnetic waves travel through the empty space and it travels very quickly to be about 3 x 108 m/s. 

 

Electromagnetic Spectrum – Ultraviolet Rays

Ultraviolet rays are the part of the Electromagnetic Spectrum ranging from the end of the visible light range to the X-ray region. It is harmful rays as a continuous effect on humans can cause skin and eye disorders. Moreover, it is the source of Vitamin D, plays an important role in human growth.

 

A large amount of UV rays coming from the sun is absorbed by the ozone layer in the atmosphere. Some other sources of UV rays are black lights, mercury lamps, and tanning lights.

 

Wavelength and Frequency of Ultraviolet Rays

Since all the electromagnetic waves travel at different speeds through the vacuum, their wavelength and frequency vary.

 

The frequency of a wave is defined as the number of times it repeats in a second. Its unit is Hertz. In the case of electromagnetic waves, the wavelength is measured in units of nanometres.

 

Ultraviolet rays have a shorter wavelength when compared with visible light and so we are not able to see in our naked eyes.

 

Ultraviolet rays were present in the wavelength range from around 10 nm to around 400 nm. It has a frequency ranging between 800 THz to 30 PHz.

 

According to physics, UV radiation is divided into four regions – 

• Near (400 – 300 nm)

• Middle (300 – 200 nm)

• Far (200 – 100 nm)

• Extreme (below 100 nm)

 

On the interaction of ultraviolet radiation wavelength with biological materials, it is divided into three divisions – 

• UVA (400nm – 315 nm) 

• UVB (315nm – 280 nm) 

• UVC (280nm – 100 nm)

 

The three types of UV radiation have been classified accordingly in respect to their wavelength. They differ in their biological activity, and to the extent of which they can penetrate the skin. The shorter the wavelength is, the more harmful the UV radiation has to be. However, shorter wavelength UV radiation is less able to penetrate into the skin.

 

The UV region covers the wavelength range in between 100-400 nm and is divided into three bands:

• UVA is (315-400 nm)

• UVB is  (280-315 nm)

• UVC is (100-280 nm).

 

Short wavelength UVC is certainly the most damaging lot of UV radiation. However, it is completely filtered by the atmosphere, and it does not reach the surface of the earth generally.

 

Medium wavelength UVB is very biologically active but it cannot penetrate beyond the superficial layers of the skin. It is responsible for the delayed tanning, and burning of the skin. In addition to these types of short term effects, it enhances early skin aging and significantly promotes the development of various skin cancers. Most solar UVB is filtered by the atmospheric layer.

 

The relatively long wavelength UV A accounts for approximately more than ninety percent of the UV radiation reaching the Earth’s surface. 

 

UV levels vary according to the height of the sun in the sky, and in mid latitudes. It is highest during the summer months during the four hour period around 12noon. During this time period, the rays of the sun take the most direct path to the earth. In contrast, during the period of early morning or late afternoon hours the sun’s rays pass at a greater angle throughout the atmospheric sphere. Much more of the UV radiation is absorbed, and the less reaches the Earth’s surface. UV levels are the highest under most cloudless skies, and cloud’s cover reduces a person’s exposure alternatively. However, light or thin clouds have little effect, and may even enhance the amount of UV levels because of scattering effect. Let’s not be fooled by an overcast day or a cool breeze, even a long stay in open shade, between buildings, may give a sensitive person a major sunburn on a day with high UV levels. With increasing altitude less, the atmosphere is able to absorb the UV radiation. With every 1000 m in altitude, UV levels increase by about ten percent. UV levels are higher when it is closer to the equator.

 

Uses of UV Rays

UV light is found in nature from sunlight and the application of sunlight is present in every field. It is present in both commercial and industrial purposes. Generally, it is used in purifying air, water treatment, skin treatment, indoor gardening, things identifying, and more uses by UV lamps.

 

UV rays are used in a wide range, ranging from medical therapy to photography. 

 

UV Light in Tanning

When your body skin is exposed to UVB rays, your body produces a pigment called melanin, which absorbs UV rays and results in heat in your skin.

 

When the body sends this melanin into besides cells, your body goes black.

In the same way, tanning booths use man-made UV light lamps, which pass an electric current through a gas (vaporized mercury gas ).

 

UV Light in Chemistry

In chemistry, UV light is used to analyze the compound’s chemical structure through its color change. A spectrophotometer is a machine used here, it passes a UV light beam into the solution. It shows how much of the UV radiation is absorbed with the observation of color change in the solution. It is widely used in the testing of water quality, and also in hospitals, food industry. 

 

Ultraviolet Light in Indoor Gardening

UV light plays a major role in the production of polyphenols. It is a plant used in the prevention of cancer and also for a young look. Moreover, it helps in improving the medicinal properties of cannabis.

 

UV lights are used in the production of polyphenols. It is a very beneficial plant and is said to prevent cancer. It can also make you look young. It can help in raisin production as well. It can also help in the production of medical cannabis. In fact, the UV light helps in improving the medicinal properties of cannabis.

 

Uses of Ultraviolet Rays in Biology

Ultraviolet
Rays in Killing Cells

UV light kills cells of the human body by damaging their DNA. When a UV light falls on the body, it initiates a reaction between two molecules of thymine, which is responsible for making DNA.

 

Then remove the two bases and nucleotides are filled in between the gaps.

 

In case the UV light is exposed for a longer time, the more thymine dimers are formed in the DNA.

 

The risk of getting incorrect repairs also increases. If it happens, the cell cannot continue its actual work. Depending upon the location of damage, cells are created from healthy cells, or else it will die if it undergoes widespread damage.

 

UV Radiation in Clinical

UV radiation is used in the treatment of psoriasis, and in recent years UV rays are used for the treatment of dermatological conditions.

 

In chronic open wounds, UV is used as an occasional component. Usually, UV rays are used in the treatment of skin disorders.