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# X-Ray Attenuation watch

1. When x-rays are absorbed by a particular material their intensity falls to 50% after travelling a distance of 4.5cm in the material.
a) What percentage of the original intensity emerges when these x-rays pass through a slab of the same material of thickness 18cm?
This is a guided question but i'm struggling on filling out some of the words:

Since the intensity decays exponentially it will have a constant half life so the intensity halves every "4.5" cm. 18cm corresponds to ....... thicknesses so the intensity will be reduced to 1/2n where n = "4"? The transmitted intensity is therefore ...................

where "" is my attempt at the right word for the gap.
2. First gap: How many 4.5s are there in 18?

Looks like the bit in the middle is complete and correct,

SO the final bit, you half it 4 times, just as though it were 4 half lives

BTW you've mentioned 'constant half life' up there, you mean (I'm sure) constant half thickness.
3. (Original post by phys981)
First gap: How many 4.5s are there in 18?

Looks like the bit in the middle is complete and correct,

SO the final bit, you half it 4 times, just as though it were 4 half lives

BTW you've mentioned 'constant half life' up there, you mean (I'm sure) constant half thickness.
Thank you and yeah I realise that half life is misleading

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