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Penetrating ability of electromagnetic radiation

Different kinds of electromagnetic radiation have different penetrabilities. For example, if we take the human body as the object. Infrared light is emitted by the human body. Visible light is reflected off the surface of the human body, ultra-violet light (from sunlight) damages the skin, but X-rays are able to penetrate the skin and bone and allow for pictures of the inside of the human body to be taken.

If we compare the energy of visible light to the energy of X-rays, we find that X-rays have a much higher energy. Usually, kinds of electromagnetic radiation with higher energy have higher penetrabilities than those with low energies.

Certain kinds of electromagnetic radiation such as ultra-violet radiation, X-rays and gamma rays are very dangerous. Radiation such as these are called ionising radiation. Ionising radiation transfers energy as it passes through matter, breaking molecular bonds and creating ions.

Excessive exposure to radiation, including sunlight, X-rays and all nuclear radiation, can cause destruction of biological tissue.

Ultraviolet(uv) radiation and the skin

UVA and UVB are different ranges of frequencies for ultraviolet (UV) light. UVA and UVB can damage collagen fibres which results in the speeding up skin aging. In general, UVA is the least harmful, but it can contribute to the aging of skin, DNA damage and possibly skin cancer. It penetrates deeply and does not cause sunburn. Because it does not cause reddening of the skin (erythema) it cannot be measured in the SPF testing. There is no good clinical measurement of the blocking of UVA radiation, but it is important that sunscreen block both UVA and UVB.

UVB light can cause skin cancer. The radiation excites DNA molecules in skin cells, resulting in possible mutations, which can cause cancer. This cancer connection is one reason for concern about ozone depletion and the ozone hole.

As a defense against UV radiation, the body tans when exposed to moderate (depending on skin type) levels of radiation by releasing the brown pigment melanin. This helps to block UV penetration and prevent damage to the vulnerable skin tissues deeper down. Suntan lotion, often referred to as sunblock or sunscreen, partly blocks UV and is widely available. Most of these products contain an SPF rating that describes the amount of protection given. This protection, however, applies only to UVB rays responsible for sunburn and not to UVA rays that penetrate more deeply into the skin and may also be responsible for causing cancer and wrinkles. Some sunscreen lotion now includes compounds such as titanium dioxide which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include zinc oxide and avobenzone.

What makes a good sunscreen?

  • UVB protection: Padimate O, Homosalate, Octisalate (octyl salicylate), Octinoxate (octyl methoxycinnamate)
  • UVA protection: Avobenzone
  • UVA/UVB protection: Octocrylene, titanium dioxide, zinc oxide, Mexoryl (ecamsule)

Questions & Answers

why mass not change
Allan Reply
what is different between work and power in details
Andiswa Reply
When a force is exerted to an object and causes it to move in the direction of the force the work is done whereas power is the rate at which work is done.
ISRAEL
can you please help me to understand this topic of work and power
Hlayiselo
i also want to be helped
Tobeka
Why is alcohol flameable?
Moloto Reply
What is interconversion reaction for? ... under substitution reaction
Moloto
how can u tell whether the compound is an alkane, alkene or alkyne
Imagine Reply
alkane compounds are saturated, consists of single bonds between atoms and alkenes are unsaturated consists of one double bond between two adjacent carbon atoms .alkynes are also unsaturated but they consists of a triple bond between 2 adjacent carbon atoms.
Andile
you can tell simple by looking at the bonds which exist between the carbon-carbon atoms of the compound, so if a compound consists of double bond between its carbon-carbon atoms it is an alkene etc.
Tatyana
can it say it cause I understand it better
Tobeka Reply
Hey, what is momentum?
Inocent Reply
the product of mass n its velocity
Albert
And what's simple harmonic?
Inocent
What is organic compounds
Gaba Reply
are compounds which consists of carbon atoms
Mkhize
Thanks bro
Gaba
How many industrial processes are there?
Sheron Reply
A homologous group is a group with the same amount of electrons in the outermost shell.
Duncan Reply
What are hydrocarbons
Lindiwe Reply
Its a compound of hydrogen and carbon atoms
Luyanda
do hydrocarbons get unsaturated?
Mandi Reply
yes
Thembi
they are saturated
Sinoty
Yes
Gugu
what is monomer
Vuyo Reply
what is polymerism
Tobeka
I think a polymer is a chemical compound with molecules bonded together in long, repeating chains. Because of their structure, polymers have unique properties that can be tailored for different uses.
Kagiso
what about a monomer ?
Louis
monomers are the building blocks of polymer.
Nandipha
which essays are expected in march exams
Qiniso Reply
what do you look at when you want to successfully compare the boiling points of two|three organic molecules
FIN Reply
1-check the homologous group 2-number of carbons or chain length n their intermolecular forces between the bonds
Lesego
why are alkanes none as primary
Babulele Reply
meant to say known as primary alchols
Babulele
because there is only 1 OH attached to carbon and carbon
Sinoty

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Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
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