how do u investigate how the range of alpha particles in air is affected by air pressure?

Like..a method and what materials that wud be used.

Place an alpha source (constant source) at one end of a tube, a detector at the other end of the tube, and have a valve assembly attached to the tube such that air pressure can be manipulated. Then count the alpha particles for a specificed amount of time at different pressures of air in the tube.

You only need paper and pencil.

You can take the range to be the collsion length, i.e. the average distance the alpha travels before suffering a collision:

L = 1/(sigma n)

L is the range, sigma the cross section for collisions of alphas with nuclei of atoms in the air (Given by Rutherford's formula), and n is the density (number of nuclei per cubic meter).

You see that the range is inversely proportional to the density. According to the ideal gas law:

P = n k T

So, if we keep temperature the same, the range should be inversely proportional to air pressure.

I SEE the sense in both concepts... but i'm a bit foggy as to count's approach.

For Dr.Bob...what equation would i need? i want to plot a graph that would deduce the relationship between the distance and the pressure.

The same for COUNT...how could i plot a graph to show this relationship...its a bit foggy

also...is there an alternate to the valve assembly? its kind of hard to depict one in a diagram...i'm required to design a lab to do this

Ah, I suppose you could get away without a valve by adjusting your compressor to give more or less pressure, but it is a lot easier with a valve.

The count gave you the graph you should come up with.
L = 1/(sigma P/kT)
L is your mean range
sigma k and T are constants in your experiment
so
L = c/P

you will get a bunch of L and P points. Plot them on your graph. Sort of hyperbolic.
to get c
graph log L plus log (P)
log L = log c - log P
log L + log P = log c

LOL - good question. If you increase the pressure by increasing the temperature in a closed container, you do not change the density, which is what is important in your experiment.

I guess what I am saying is read what the Count told you again. It is the density of the gas that is important to the range, not the pressure. If the pressure increases due to putting more molecules in the box, that changes the density.

what is c in the eqn L=c/P?

L = c/P

you will get a bunch of L and P points. Plot them on your graph. Sort of hyperbolic.
to get c
graph log L plus log (P)
log L = log c - log P
log L + log P = log c

Explain that part please...i'm not as sharp as i should be...this is kinda unfamiliar

Increasing T will not do it. The main difference between my method and the Counts method is mine is experimentally determined and his is a pencil and paper procedure.

okay ..i get it...so the same equations apply to your method?

Yes, but in the experimental method you are generating the data from scratch, more or less, and in the pencil and paper method you are using data that is already available.