What can Ultraviolet radiation pass?

[AJ153]

I keep hearing that windows filter Sun UV rays? some say its 99% others say its 50%, I know windows filter UV-B, but not all of UV-A. Lets say are controlled factor is a sunny morning (fall-winter season in Canada) morning when UV's are the weakest, and fall-winter when there even weaker. Would UV penetrate through a window? If so lets say I filter it by covering the window with construction paper (material used for shipping envelopes)? How strong would the UV Rays be if even existent? Would any of the following below be effected?

reason why I want too know

-Having a bed for a babe next to a window in the early morning?

-People with sensitive skin

- fear of Indoor items/clothing that sit next to windows form fading.

[John Cuthber]

Glass is made to slightly different recipes and specifications so it's hard to generalise.

If you really want to block UV then polycarbonate is good at that.

On the other hand, how good an idea is it to stop babies getting sunshine?

http://en.wikipedia.org/wiki/Rickets

[AJ153]

 

 

Can Sun UV-A and UV-B penetrate through cardboard? If I were to say store something that UV sensitive (fades very fast to UV rays). Would it be safe?

[John Cuthber]

Cardboard (especially if it's black) would be a good way to block UV, but if you want to be really sure use aluminium foil.

[AJ153]

interesting, Gosh I wish I still had my chemistry/physics note book, I remember taking notes on UV radiation. Would me just rapping the UV sensitive objects with cloth or adding another box inside the box protect it? My mom would not approve using her cooking stuff, for my artwork.

[John Cuthber]

Pretty much anything that blocks visible light will block UV.

A black cloth would work fine.

[AJ153]

What can UV radiation from the sun pass through? Can it pass through any of these materials Opaque/semi Opaque

 

- House glass (ones in everyday normal windows)

- Cardboard (used for packaging)

- Paper

- Plastic

- Water

- Cloth (Like window blinds)

- Metal

- Umbrella

 

 

 

As I grow older I'm more curious in UV protection for home,car, and outdoors since my family has a history of skin problems caused by sun UV Radiation, I remember learning this in Chemistry class, but I totally forgot about what UV can penetrate through.

 

Thank you for reading.

Edited January 11, 2013 by AJ153

[JohnCli]

It can pass through anything transparent,how ever there are also exceptions.

The only radiations that can pass through matter easily are X-ray,Alpha,Beta and Gamma Radiations and any other things that may be discovered that has more energy inside them.

Such exceptions are Polarized crystals that do not allow UV light to pass.

 

- House glass (ones in everyday normal windows)

yes

 

- Cardboard (used for packaging)

Depends on thickness

 

- Paper

Depends on thickness

 

- Plastic

Dot

 

- Water

Yes

 

- Cloth (Like window blinds)

Dot and composition

 

- Metal

No

 

- Umbrella

Pure black = no Transparent ordinary plastic = yes

Edited January 11, 2013 by JohnCli

[swansont]

It can pass through anything transparent,how ever there are also exceptions.

The only radiations that can pass through matter easily are X-ray,Alpha,Beta and Gamma Radiations and any other things that may be discovered that has more energy inside them.

 

Um, no. Beta and especially alpha tend NOT to penetrate very far because they are charged and interact strongly with matter. High-energy betas might penetrate glass, but alphas would not.

 

 

- House glass (ones in everyday normal windows)

yes

 

Depends on the type of glass and region of the UV. Common glass tends to cut off around 300 nm.

 

http://www.shimadzu.com/an/industry/ceramicsmetalsmining/chem0501005.htm

[AJ153]

 

Um, no. Beta and especially alpha tend NOT to penetrate very far because they are charged and interact strongly with matter. High-energy betas might penetrate glass, but alphas would not.

 

 

Depends on the type of glass and region of the UV. Common glass tends to cut off around 300 nm.

 

http://www.shimadzu.com/an/industry/ceramicsmetalsmining/chem0501005.htm

 

Thank you for your replys, many thanks John! I think this information will aid me for better heath and prevent my familys skin problems with UV! Also additional protection of invested material (furniture,antics,paintings) from UV damage, In a study UV damage is too house hold things are the following

 

So scientifically UV Radiation (lets say A) will not pass solid opaque material or any sort of matter depending on thickness? I remember water either reflects the UV or it goes only so far (e.g. the ocean). With glass I remember in 8th grade chem class our teacher told us glass filters a good amount of UV. Also I live pretty far from the equator (Chicago Land area) and being the winter time with no snow (UV reflection) the sun shines down onto my room only around 7:30-10 A.M when the sun is at its weakest. So I'm not worrying to much, but I do have a mild OCD. Which is why I love science since it answers all my OCDness.

 

The thickness I'm talking about for cardboard is like this

 

and the paper Im talking about is like this

 

 

 

 

Reasons why I would like too know is because aside from studying science I also seek art to calm my OCD, the only thing is I want to store my paintings from the harmful UV radiation, and boxs and packaging paper envelopes is all I have really. I really want to know if this is enough UV protection giving the variables of morning UV rays near Chicago, IL in the middle of the winter. Again many thanks for taking the time to answer my questions! I really do appreciate this!

Edited January 11, 2013 by AJ153

[swansont]

!

Moderator Note

Note: multiple threads merged

[John Cuthber]

1 It can pass through anything transparent,how ever there are also exceptions.

2 The only radiations that can pass through matter easily are X-ray,Alpha,Beta and Gamma Radiations and any other things that may be discovered that has more energy inside them.

 

3 Such exceptions are Polarized crystals that do not allow UV light to pass.

 

4 - House glass (ones in everyday normal windows)

yes

 

5 - Cardboard (used for packaging)

Depends on thickness

 

6 - Paper

Depends on thickness

 

7- Plastic

Dot

 

8- Water

Yes

 

9- Cloth (Like window blinds)

Dot and composition

 

10- Metal

No

 

11- Umbrella

Pure black = no Transparent ordinary plastic = yes

1 is meaningless since it says "everything apart from some things"

2 is clearly nonsense, if it were true then, for example, you wouldn't be able to see through air.

3 No, water is an obvious exception.

4 Ordinary glass is quite good at blocking UV, especially short wavelength UV.

5 Any cardboard thick enough to be used for packaging is likely to be pretty much completely opaque to UV. It will generally block UV better than it will block visible light so, if you can't see light through it, it's going to block UV.

6 Paper isn't going to work as well as card, but the UV brighteners in most paper will still block a lot of the UV.

7 Some plastics are intrinsically pretty transparent to UV (polythene and polypropylene for example): other are not (polycarbonate and PET are opaque to most UV. The fact that most plastics contain additives makes it difficult to guess how any given bit of plastic will stop UV.

8 Yes! he finally got one right ( though it contradicts 3)

9 It depends more on the openness of the weave than anything else, a thick black felt will block UV rather well. A string vest won't, because it's full of holes.

10 Wow! another one right.

11 I might bet on a plasticised PVC umbrella blocking UV better than a cheap cloth one. If you can see through the holes in the cloth, it won't work very well.

[AJ153]

Mr.Cuthber you have relied my OCD-ness to UV! Many thanks to the explanations! I gained alot of knowledge, and really do appreciate it! Love the humor to the other John

Edited January 12, 2013 by AJ153

[JohnCli]

 

Um, no. Beta and especially alpha tend NOT to penetrate very far because they are charged and interact strongly with matter. High-energy betas might penetrate glass, but alphas would not.

 

 

Depends on the type of glass and region of the UV. Common glass tends to cut off around 300 nm.

 

http://www.shimadzu.com/an/industry/ceramicsmetalsmining/chem0501005.htm

 

Thanks for the correction

[StringJunky]

 

Depends on the type of glass and region of the UV. Common glass tends to cut off around 300 nm.

 

Cuts off wavelengths shorter than this?

[John Cuthber]

Pretty much, yes.

It depends on the glass and the thickness, but on the whole windons are pretty much opaque to UV from 300nm to the soft Xray region.

[StringJunky]

Thanks JC.

 

At the QED level, this is because the electron receiving the incoming photon is sufficiently energised to reach the next energy level so the uv photon doesn't carry on passing through...is this right?

[AJ153]

Can someone confirm if his answer is correct? UV has interesting proprieties compared to Alpha,Beta,Gamma Rays

 

Question:

I am currently taking first year physics in university and something that we were learning about peaked my interest. I know that alpha radiation is blocked by almost everything, beta by metallic and thicker material, and gamma by really thick materials, like a cm of lead. I was curious what completely blocks out uv radiation. I know that its non-ionizing so its not really like alpha, beta and gamma radiation. And clothing blocks some, but not 100% of it, unless you're wearing layers, or specially formatted fabrics. But does something like bristol board or a heavy paper block it 100%? I'm not sure if you know the answer, but I thought I'd give it a try. Thanks

 

Answer:

Ultraviolet is broken into three bands based on wavelength, UVA, UVB, and UVC:

UVA 400 nm - 320 nm
UVB 320 nm - 290 nm
UVC 290 nm - 100 nm

Materials can act very differently from one band to another. For instance, this page discusses sunscreen:

http://www.fda.gov/fdac/features/2000/400_sun.html

In general, the penetration depth of light into a material is a function of the wavelength of light. This rule begins to break down in the shorter-wavelength UV due to the high power of the photons. However, this is why very thin layers easily block UV light (for example, sunscreen or films on your sunglasses).

Clothing is not a very good UV blocker because of gaps between fibers. Synthetic materials are also frequently transparent to UV, but I think most organic dyes are good UV absorbers, but they also break down under prolonged exposure (due to ionizing).

While not a definitive result, I can safely say that plain white paper is not a good blocker from experience in the lab. Anything thick, with dye (like bristol board) will block transmission of nearly 100% of UV light. The board will break down under prolonged exposure.

Best,
Curtis

 

 

Source: .allexperts.com/q/Physics

Edited January 13, 2013 by AJ153

[John Cuthber]

I think what he says is pretty much correct.

[swansont]

Can someone confirm if his answer is correct? UV has interesting proprieties compared to Alpha,Beta,Gamma Rays

 

Question:

I am currently taking first year physics in university and something that we were learning about peaked my interest. I know that alpha radiation is blocked by almost everything, beta by metallic and thicker material, and gamma by really thick materials, like a cm of lead. I was curious what completely blocks out uv radiation. I know that its non-ionizing so its not really like alpha, beta and gamma radiation. And clothing blocks some, but not 100% of it, unless you're wearing layers, or specially formatted fabrics. But does something like bristol board or a heavy paper block it 100%? I'm not sure if you know the answer, but I thought I'd give it a try. Thanks

 

UV is ionizing radiation. The difference between it and alphas and betas is that the latter two are charged, which gives them a maximum penetration depth in a material. Gammas (and UV photons) are attenuated, but not completely blocked by a material — they undergo an exponential drop in their flux. So it doesn't drop to zero, it just drops to a level where you don't worry about it anymore.

 

e.g. the attenuation coefficient for lead at around 3 MeV is about 0.45 cm^-1, meaning an incoming flux incident upon a 1 cm thickness of lead will be attenuated to e^-0.45, or about 64% of its original value.

[Enthalpy]

I can tell for sure that a clear car window protects from Sunlight burns.

 

I had a burn in Guyana but decided not to use a skin protection because I was in a car, and after several hours of clear weather (4° from Equator, serious there) it had not worsened a bit. Convincing synthetic experimental proof for me.

[maryamasim]

1 is meaningless since it says "everything apart from some things"

2 is clearly nonsense, if it were true then, for example, you wouldn't be able to see through air.

3 No, water is an obvious exception.

4 Ordinary glass is quite good at blocking UV, especially short wavelength UV.

5 Any cardboard thick enough to be used for packaging is likely to be pretty much completely opaque to UV. It will generally block UV better than it will block visible light so, if you can't see light through it, it's going to block UV.

6 Paper isn't going to work as well as card, but the UV brighteners in most paper will still block a lot of the UV.

7 Some plastics are intrinsically pretty transparent to UV (polythene and polypropylene for example): other are not (polycarbonate and PET are opaque to most UV. The fact that most plastics contain additives makes it difficult to guess how any given bit of plastic will stop UV.

8 Yes! he finally got one right ( though it contradicts 3)

9 It depends more on the openness of the weave than anything else, a thick black felt will block UV rather well. A string vest won't, because it's full of holes.

10 Wow! another one right.

11 I might bet on a plasticised PVC umbrella blocking UV better than a cheap cloth one. If you can see through the holes in the cloth, it won't work very well.

Even I have heard that anything that can block light will be able to block UV radiation. But I am a bit confused. What I know is that UV rays have a shorter wavelength than light rays that's why they come before light in the spectrum. That means that they penetrate better as compared to light rays. So does that mean even if light is being blocked that does not mean UV radiation is being blocked?

[swansont]

Even I have heard that anything that can block light will be able to block UV radiation. But I am a bit confused. What I know is that UV rays have a shorter wavelength than light rays that's why they come before light in the spectrum. That means that they penetrate better as compared to light rays. So does that mean even if light is being blocked that does not mean UV radiation is being blocked?

 

Not necessarily. Interaction probability of light depends on the material and its structure. At lower energy a material might block an EM wave because the electrons are very responsive to it, but at high enough frequency the responsiveness goes down. When you get into the UV you have ionizing radiation, and relative transparency has less to do with having a large bandgap (as with clear materials) and more to do with how easily you ionize the electrons. It is possible you could find a material that is opaque to visible light because of the bandgap, but relatively transparent to UV because there are few electrons per unit volume to ionize.

 

Materials that fit the description do exist

http://en.wikipedia.org/wiki/Wood%27s_glass

 

You could also probably coat a transparent material to make it reflect and absorb in the visible but still transmit UV

[John Cuthber]

I think what they are talking about is the fact that Xrays go through stuff,

Edited February 17, 2013 by John Cuthber