Homework Help: Penetrating power of radiation questions

1. Jun 13, 2013

tg22542

1. The problem statement, all variables and given/known data

My questions relate to a worksheet given which includes a data table displaying results from putting a source of beta radiation near a Geiger-Mueller tube, and recording the Beta radioactivity through the shielding. It started off with the radiation going through nothing, where it was 1000 counts/min, then it shows data measured through cardboard, aluminum and lead. Then 2 sheets, then 3 etc. But the data should not be relevant to these questions really. If you think I should include the data table, let me know and I will do so.

1) What was the purpose of measuring the activity with no shielding material in place?

2) Why was it important to keep the distance between the source and the Geiger-Mueller tube constant

3) If you repeat the exercise using gamma radiation (with unshielded reading of 1000count/min)| instead of beta radiation, which numbers in the table would change? Would they be higher or lower?

2. Relevant equations

none

3. The attempt at a solution

1) We would do this in order to find the beta radioactivity amount that is given off by our source with no obstructions

2) We need to keep the distance constant because if we changed the distance our data would be different. If we moved it farther away we could have less count/min <--- but i dont know why, or if this is true. not sure what else to say

3) Gamma radiation would penetrate through the material much easier than beta. Gamma radiation is electromagnetic radiation of high energy, thus is stronger. <-- Need more on this answer as well.

Any help will be greatly appreciated,
Thanks!

2. Jun 13, 2013

voko

2) A light bulb appears brighter when it is closer. A loudspeaker sounds louder when one is nearby. Why is that so?

3. Jun 13, 2013

tg22542

Because you're closer to the strongest waves?

4. Jun 13, 2013

voko

Let's assume that for a second. Where and why do the strongest waves disappear? And why are they at the source to begin with?

5. Jun 13, 2013

tg22542

They become weaker and less visible as they travel further. They are at the source because it is creating energy and the waves are the visible energy

6. Jun 13, 2013

voko

But why do they become weaker?

7. Jun 13, 2013

tg22542

Because the photons are being absorbed by different atoms thus weakening the visible energy?

8. Jun 13, 2013

voko

Imagine this is happening in vacuum. No absorption.

Actually, you don't even have to imagine this.

Look at the stars. Look at the Sun. They are all in a very good vacuum. Yet the Sun seems so much brighter than any star, even if many of those stars emit a lot more light than does the Sun.