An experiment showing an increase with dilution in a physical parameter

1981 ◽  
Vol 70 (03) ◽  
pp. 129-135 ◽  
Author(s):  
S.J. Hadley

SummaryA simple apparatus is described with which it is possible to measure the phase shift induced in a high frequency alternating current by a cell containing a dilute solution of an electrolyte.This phase shift is seen to INCREASE WITH DILUTION up to a limit determined by the electrolyte chosen (but usually within the range 10−4 to 10−6) and then to decrease with further dilution to zero.Solutions of salts and sugar in water and dilute alcohol are investigated.The findings are discussed.

A method has been rediscovered, and developed in theory and practice, for optical observation of the earliest stages of diffusion across an initially sharp boundary between a dilute solution and a solvent. It enables the diffusion constant of a monodisperse solute to be measured about fifty times as quickly as by other methods, at lower concentration and possibly with greater accuracy; it should therefore be particularly valuable for the study of high molecular substances. The method is based on the interference pattern which is formed when monochromatic light from a horizontal slit is focused after passing through a cell where diffusion is occurring. The pattern, a set of horizontal bands, contracts towards the optic axis as diffusion proceeds, at a rate from which the diffusion constant can be calculated. By counting the bands in the pattern the refractive increment of the solute can be determined. The sharp initial boundary is obtained by flowing the solution and solvent out through a common narrow horizontal slit. The construction, calibration, and use of the apparatus are described.


2021 ◽  
pp. 717-721
Author(s):  
D. Serrano-Muñoz ◽  
J. Gómez-Soriano ◽  
D. Martín-Caro ◽  
R. López-Peco ◽  
J. Taylor ◽  
...  

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1887
Author(s):  
Daniel Puerto ◽  
Sergi Gallego ◽  
Jorge Francés ◽  
Andrés Márquez ◽  
Inmaculada Pascual ◽  
...  

Photopolymers can be used to fabricate different holographic optical elements, although maximization of the phase-shift in photopolymers has been a challenge for the last few decades. Different material compositions and irradiation conditions have been studied in order to achieve it. One of the main conclusions has been that with continuous laser exposure better results are achieved. However, our results show for the first time that higher phase-shift can be achieved using a pulsed laser. The study has been conducted with crosslinked acrylamide-based photopolymers exposed with a pulsed laser (532 nm). The increment of the phase-shift between the pulsed laser and continuous laser exposure is 17%, achieving a maximum phase-shift of 3π radians and a refractive index shift of 0.0084 at the zero spatial frequency limit, where monomer diffusion does not take place. This allows this photopolymer to be used in large-scale manufacturing.


1905 ◽  
Vol 74 (497-506) ◽  
pp. 476-487 ◽  
Author(s):  
John Ambrose Fleming

An electric oscillation being an alternating current of very high frequency, cannot directly affect an ordinary movable coil or movable needle galvanometer. Appliances generally used for detecting electric waves or electric oscillations are, therefore, in fact, alternating current instruments, and must depend for their action upon some property which is independent of the direction of the current, such as the heating effect or magnetizing force. The coherer used in Hertzian wave research is not metrical, since the action is merely catastrophic or accidental, and bears no very definite relation to the energy of the oscillation which starts it. Even the demagnetising action of electric oscillations, though more definite in operation than the contact action at loose joints, is far from being all that is required for quantitative research.


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