is Pb 100% effective in absorbing radioactivity, even if it is extremely thick?

Answer 1

To the previous answerer: One doesn't have to be pedantic and scolding to answer an imperfectly phrased question when a flexible frame of mind will do. The quick answer is no, it's never 100% effective. Because of its density, lead is a good absorber of electromagnetic radiation such as X-rays and gamma rays, but a poor absorber of neutrons (see ref. 1). Because of its poor neutron absorption it does not become significantly radioactive as an efficient absorber would. Its attenuation of EM radiation is an exponential function of thickness; e.g., 2 cm thickness will allow the square of the fraction of incident radiation that one cm does. So if one cm allows 1/2 the radiation to pass, 2 cm will allow 1/4.
According to wiki (ref. 2), the following thicknesses of various materials will attenuate gamma rays by 1/2:
9 cm (3.6 inches) of packed dirt or
6 cm (2.4 inches) of concrete,
1 cm (0.4 inches) of lead,
0.2 cm (0.08 inches) of depleted uranium,
150 m (500 ft) of air.
Other emanations resulting from radioactivity are alpha particles (helium nuclei) and beta particles (electrons). These are fairly easily stopped by small thicknesses of material.

Answer 2

Huh? I don't think you know enough of the basics to be asking this sort of quests ion.

1) Radioactivity is a state, it is not something to be absorbed. Talking about absorbing radioactivity is like talking about absorbing height. Radioactivity and height are both properties that objects have. You can't absorb those properties, you can only measure them.

2) You can absorb RADIATION, but radiation and radioactivity are NOT interchangeable terms.

3) The biggest danger from radioactivity comes form inhaling particles of radioactive dust or gas, not from emitted radiation per se. The best way to avoid the harmful effects of radioactivity in many circumstances is simply to wear a dust mask.

4)Radiation simply refers to energy that is radiated. Most radiation is harmless. A candle produces radiation, lots of it. So does a lightbulb. so does the human body. Only some very specific types of radiation are dangerous. Many types of radiation can be blocked quite effectively by a sheet of paper.

5)NOTHING is 100% effective in absorbing radiation. Radiation operates at a quantum level, and that means that all interactions are probabilistic. Nothing is certain.

5) Lead isn't the best material for blocking dangerous radiation, not by a long way. Gold and uranium for example are much better. Lead is in radiation shielding used because it is cheap and relatively safe to work with, not because it is perfectly effective.

6) The ability of lead,or any other material, to block radiation is related to thickness. As thickness increases the absorption increases. Lead 1/2 inch thick is no more effective than 2" of steel or 12" of brick.

Now that you know all that would you like to work out what question you intended to ask and resubmit?

Answer 3

It's never 100%, but it gets closer and closer to 100% the thicker the lead.

Effectiveness is given by
100% * [1 - exp(-A*x)],
where x is the thickness of the lead (for example, in cm)
and A is a coefficient that depends on the specific type of radiation. As x gets larger, the term "exp(-A*x)" approaches zero and the effectiveness approaches 100%.

You can try plugging a few numbers into a calculator to see this. Use A=1, and try x = 0, 1, 2, 4, 8. The "exp" function is probably labelled as e^x on your calculator. Youl see that the effectiveness is zero when there is no lead (x = 0), and is 99.966...% for x = 8.

(And don't forget that there is a minus sign in exp(-A*x))

Good luck

Answer 4

The thicker the lead, the better protection it affords...