The theory of optics / by Paul Drude ; translated from the German by C. Riborg Mann and Robert A. Millikan.

Date:
1902
Catalogue details

Licence: In copyright

Credit: The theory of optics / by Paul Drude ; translated from the German by C. Riborg Mann and Robert A. Millikan. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    between Qx and Q2, a the distance of the line d from the line PqP, and p the distance of a point P from the point PQ, which lies on the perpendicular erected at the middle of d} r? = «* + (W + Pf. r} = a* + (\d - p)\ i.e. r* - r* = (r, + r2)(r, - r2) = 2dp, or since rx -|- r2 is approximately equal to 2a when p and d are small in comparison with a, it follows that rx — r2 = dp \ a, i.e. darkness occurs at the points a_ a 3^ ± d‘2 ’ ± d ' 2 P a ±d 2 etc. (13) Hence, if the light be monochromatic, interference fringes will appear on a screen held at a distance a from the line d, and the constant distance between these fringes will be a\ : d. If white light is used, colored fringes will appear upon the screen since the different colors contained in white light, on account of their different wave lengths, produce points of maxi- mum and minimum brightness at different places upon the screen. But at the point P0 there will be no color, since there all the colors have a maximum brightness (rx — r2— o). The distance d between the virtual sources may be calcu- lated from the position of the actual source Q with respect to the mirrors and the angle between the mirrors. This angle must be very small (only a few minutes) in order that d may