shutter speed varies inversely as square of aperture setting

wasn't sure were to put this i know its not exactly advanced but is to me , only place to post that made sence so tell me if i'm wrongh

year 10 gcse question: The shutter speed, S, of a camera varies inversely as the square of the aperture setting, f. When f= 8, S= 125

a) find a formula for S in terms of f.

b) Hence, or otherwise calculate the value of S when f= 4

thanks for any time anybody spends on this question

Rob

Edit: i have some answers now but am not sure if there correct so if possible could somebody answer both the questions so i can check the answers / working

Just use the formula \(\displaystyle S=\frac{k}{f^{2}}\)

Solve for k. Then you can plug in any value for f and find S.

so i would be saying for part a)

S=k/f^2
125=k/64
64*125= 8000
that k = 8000?

Yes, but find k first from the given data.

rob12341 said:

so i would be saying for part a)

S=k/f^2
125=k/64
64*125= 8000
that k = 8000?

Click to expand...

Yes, k=8000. Now you can answer f=4

so
for part b)

k=8000
f=4
S=?

S =8000/4^2 =500

thanks so much for your help and sorry for being a pain :?

a lot easier then i thought