National Physical Laboratory

About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.

The Colour Change of Monochromatic Light with Retinal Angle of Incidence

Abstract: The few previous measurements of the small change of apparent colour of a monochromatic light stimulus when its angle of incidence on the foveal retina is varied (or SC II effect), have been confined to changes of apparent hue. A differential, three-colour mixture method, with alternating instead of juxtaposed presentation of the test and comparison stimuli, has now been applied to determine the complete colour change, hue and saturation. For the main subject, the results show hue shifts of the expected kind and a small but significant supersaturation of the apparent colour of an obliquely, compared with a normally incident stimulus, in the wavelength range 485 to 510 mµ. From earlier qualitative observations, such a supersaturation appears to occur for most subjects. The SC II colour changes are attributable to differences in the directional response of the receptors associated respectively with the three colour systems of the trichromatic scheme. From the relative spectral sensitivities of these systems...

Influence of preparation method on structural and magnetic properties of nickel ferrite nanoparticles

Abstract: Nickel ferrite nanoparticles of very small size were prepared by sol-gel combustion and co-precipitation techniques. At the same annealing temperature sol-gel derived particles had bigger crystallite size. In both methods, crystallite size of the particles increased with annealing temperature. Sol-gel derived nickel ferrite particles were found to be of almost spherical shape and moderate particle size with a narrow size distribution; while co-precipitation derived particles had irregular shape and very small particle size with a wide size distribution. Nickel ferrite particles produced by sol-gel method exhibited more purity. Sol-gel synthesized nanoparticles were found to be of high saturation magnetization and hysteresis. Co-precipitation derived nickel ferrite particles, annealed at 400°C exhibited superparamagnetic nature with small saturation magnetization. Saturation magnetization increased with annealing temperature in both the methods. At the annealing temperature of 600°C, co-precipitation derived particles also became ferrimagnetic.

Measurement of absorption coefficients of Ga 0.47 In 0.53 As over the wavelength range 1.0-1.7 μm

Abstract: The absorption coefficient of p + -, p - -and n - -doped Ga 0.47 In 0.53 As layers, grown lattice-matched to InP, has been calculated over the wavelength range 1.0-1.7 μm from transmission and reflection measurements.