Question

I know it's not math...but still I'd really appreciate the help.
The graph below shows the decay of a radioactive isotope. What is the half-life of the isotope?
A. 15 seconds
B. 25 seconds
C. 40 seconds
D. 200 seconds
The graph is in an attachment. :)

Answer 1

Sorry I just didn't do the lesson...I just need somebody to explain how to find it >:P

Answer 2

Attachment, please! :)

Answer 3

Haha ^

Answer 4

look where 15 is

Answer 5

looks to me like 40

Answer 6

It;s around 40 seconds

Answer 7

Will you guys explain a wittle better ^_^
Like I don't have a CLUE how to do this.
Maybe that'll help with how you explain? :)

Answer 8

lol, this is math ;p

Answer 9

Okay, number of atoms start at 30. You want to know when it is 15(half life)

Answer 10

It's chem/physics >:P But yea sure lawls

Answer 11

Right.

Answer 12

half-life is the amount of time it takes for the current amount to be cut in half.

Answer 13

so pick any point to start with. 0,30 looks good.

Answer 14

then look for how much time goes by before it gets to half of 30.

Answer 15

that time is the half-life.

Answer 16

OHHHHHHHHHHHHHHH
Wow okay sorry about that!
THANKS!!!!!!!!!!!!!!!!!!!! :D :D :D

Answer 17

Thanks everybody that helped me!!!! :) Or at least attempted!! :)

Answer 18

Any people wanna volunteer to help me a little more if I need more explanations? :)

Answer 19

Lifetime is time when intensity (number of atoms) decreases e times.

Answer 20

Anyone wanna explain/ help on this one too? :)
Which of the following is the best definition of half-life for a radioactive substance?
A. Half of the amount of time required for all of the radioactive atoms to decay.
B. The amount of time required for half of the radioactive atoms to decay.
C. The amount of time required for each radioactive atom to decay halfway.
D. All of the above.

Answer 21

when you calculated this time, you can calculate the 1/2 time.

Answer 22

I would say A, but not sure for 100%

Answer 23

Okay.
And how would you back tht up? :)

Answer 24

I think i'll go with B.

Answer 25

That's the definition. The time required for half the atoms to decay

Answer 26

Hmmmmm
Right.
just a reminder sorry for my crappy questions.
Took little to no notes on what i DID do on this lesson >:P

Answer 27

Suppose 128 radioactive atoms have a half-life of 15 seconds. Approximately how many radioactive atoms will be left after 60 seconds?
A. 32
B. 16
C. 8
D. None
this one?

Answer 28

I think you must operate more with the e, because the lifetime must be described with exponent.

Answer 29

after 15, 64 will be left
after 30, 32 will be left
after 45, 16
after 60, 8
8 is it

Answer 30

Do you think I could just divide 128 / 15?
Because I got 8 . something something and rounded that's just 8. The same answer you got ^_^