Patrick I know your formula decribes the optimum size and distance of a pinhole sharpener, but do you think your formula could help determine the optimum size of the gap between the bead and hole of a bead-in-hole sharpener?
And thanks for disecting the formula and explaining your numbers. (I've never seen the little symbol ^ used in a formula before.) John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Patrick Powers" <[EMAIL PROTECTED]> To: "sundial" <sundial@rrz.uni-koeln.de> Sent: Wednesday, June 05, 2002 4:30 PM Subject: Re: Shadow Sharpener Again > John, I clicked 'send' on my last message without adding the detail of the > formula! > > The basic formula is actually f=(s^2)/(L), where > f is the focal length, s is the radius of the (infinitely thin!) hole and L > is the wavelength of the light. > > Sunshine has a representative wavelength of 550 nanometres. so that the > formula can be written: > > s=SQRT(f)*SQRT(550) > So, D the diameter is given by > D=2*SQRT(f) *23.452, or > D= 46.904*SQRT(f) > > But all these are in nanometres so we need to multiply by 0.001 (actually > SQRT(0.001^2) to get millimetres. Thus > > D=0.046904*SQRT(f) > > That's where the 0.047 comes from. It gives a way for calculating how a > near-perfect shadow sharpener should work when used on sundials. > > Patrick > > > > > > ------------------------------------------------------------------------- > E-Mail: [EMAIL PROTECTED] > Web: http://ourworld.compuserve.com/homepages/Patrick_Powers/ > Lat: N 51d. 49m. 09s: Long: W 00d. 21m. 53s > > - > -
