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XLVI.—On Photometric Paddle-Wheels
Published online by Cambridge University Press: 15 September 2014
Summary
This paper describes a new form of rotating photometric “sector,” capable of very accurate adjustment to any desired light-transmission value while running, and possessed of the great advantage of having its rotating part in one piece only.
A mathematical discussion of this new type of apparatus follows, in which are deduced formulæ for the intensities of the light transmitted under different conditions, and for the greatest width of the beam of light that can be employed; and a graphical tabulation of the values of these formulae in different cases is provided.
The mounting and details of an actual instrument are described; together with an additional mechanism for the purpose of automatically recording the photometric measurements obtained.
- Type
- Research Article
- Information
- Copyright
- Copyright © Royal Society of Edinburgh 1912
References
page 656 note * Proc. Roy. Soc., Series A, vol. lxxxii. p. 307, 1909.
page 661 note * On referring to the photograph of fig. 17 it will be seen that in practice the construction of the wheels of types A and A′ may be such as to reduce the air resistance considerably.
page 662 note * σ′ being the eclipse-angle of one of the actual vanes, and e being the eclipse-angle of one of the imaginary vanes, each of which must in this case be considered as consisting of a rectangle connecting the edge of a front vane to the corresponding edge of the vane behind it.
page 671 note * When dealing with small values of p greater accuracy will be obtained if AE is made equal to twice p, it being remembered that in that case the value of OL which will be obtained is twice the value of n.
page 671 note † Found from Chart II., putting a = am.
page 671 note ‡ Found from Chart I., putting a = am.
page 679 note * See the final sentence of the “Definitions” of § 1.
page 682 note * Proc. Roy. Soc. Edin., vol. xxix. p. 176, 1909.