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ultraviolet rays

Primary Information
Secondary Information

Definition

Ultraviolet rays (UV rays) are a type of electromagnetic radiation that is emitted by the sun and some artificial sources. They are invisible to the human eye, but they can be detected with special instruments.

UV rays are divided into three main types:

  • UVA rays: These rays have the longest wavelength and the lowest energy. They can penetrate the skin deeply and cause skin ageing and wrinkles.
  • UVB rays: These rays have a shorter wavelength and higher energy than UVA rays. They can cause sunburn and skin cancer.
  • UVC rays: These rays have the shortest wavelength and highest energy of the three types of UV rays. They are blocked by the ozone layer in the atmosphere and do not reach the Earth's surface.
  • UV rays can damage the skin, eyes, and immune system. They can also cause cancer.

There are a number of things that people can do to protect themselves from UV rays, including:

  • Wearing sunscreen
  • Wearing sunglasses
  • Avoiding the sun during the middle of the day
  • Staying in the shade

How can the word be used?

Ultraviolet rays are harmful to living things in high doses, but they can also be beneficial in some cases.

ultraviolet rays

Different forms of the word

Noun:

  • ultraviolet rays (invisible rays that have a shorter wavelength than visible light).
  • ultraviolet radiation (the emission of ultraviolet rays).
  • ultraviolet light (light that has a wavelength shorter than visible light).

Adjective:

  • ultraviolet (of or relating to ultraviolet rays).

Etymology

The word "ultraviolet" is made up of the Latin words "ultra" (beyond) and "violet" (purple). The word "ultraviolet" was first used in the 19th century to refer to rays that were beyond the violet end of the visible spectrum.

Question

What are ultraviolet rays?

AQA Science Exam Question and Answer

Question:

Explain what ultraviolet (UV) rays are and discuss their potential effects on human health. Describe how UV rays are categorized and the differences between UVA, UVB, and UVC rays. Provide an example of a practical application of UV rays.

Answer:

Ultraviolet (UV) rays are a type of electromagnetic radiation emitted by the sun. They have shorter wavelengths than visible light and are invisible to the human eye. UV rays are categorised into three main types: UVA, UVB, and UVC, each with distinct characteristics and effects.

UVA rays have the longest wavelengths and can penetrate the skin's deeper layers. They contribute to tanning and premature ageing of the skin. UVB rays have shorter wavelengths and primarily affect the skin's outer layers, leading to sunburn and a higher risk of skin cancer. UVC rays have the shortest wavelengths and are the most energetic, but they are mostly absorbed by the Earth's atmosphere and do not reach the surface.

Excessive exposure to UV rays can have harmful effects on human health, including sunburn, skin ageing, and an increased risk of skin cancer. It is crucial to protect the skin from UV radiation by using sunscreen, wearing protective clothing, and avoiding prolonged sun exposure.

A practical application of UV rays is in germicidal lamps, which emit UVC rays to disinfect air, water, and surfaces. UVC radiation can destroy the DNA of microorganisms, rendering them unable to reproduce and causing their death. This technology is used in healthcare settings, laboratories, and water treatment facilities to maintain hygiene and prevent the spread of infections.