A colloid consists of particles of one type of substance dispersed in another substance. Suspensions of electrically charged microspheres (microscopic spheres, such as polystyrene) in a liquid such as water can form a colloidal crystal when the microspheres arrange themselves in a regular repeating pattern under the influence of the electrostatic force. Colloidal crystals can selectively manipulate different wavelengths of visible light. Just as we can study crystalline solids by using Bragg reflection of x rays, we can study colloidal crystals through Bragg scattering of visible light from the regular arrangement of charged microspheres. Because the light is traveling through a liquid when it experiences the path differences that lead to constructive interference, it is the wavelength in the liquid that determines the angles at which Bragg reflections are seen. In one experiment, laser light with a wavelength in vacuum of 650 nm is passed through a sample of charged polystyrene spheres in water. A strong interference maximum is then observed when the incident and reflected beams make an angle of 39° with the colloidal crystal planes. When the light is passed through the bottom of the sample container, the interference maximum is observed to be at 41°; when it is passed through the top, the corresponding maximum is at 37° Part A What is the best explanation for this observation? O The microspheres are more tightly packed at the top, because they tend to float to the top of the suspension. O The maximum at the bottom corresponds to m = 2, whereas the maximum at the top corresponds to m = 11 O The increased pressure at the bottom makes the microspheres smaller there. O The microspheres are more tightly packed at the bottom, because they tend to settle in the suspension. Submit Request Answer < Return to Assignment Provide Feedback

How much energy is carried by light with a wavelength of λ = 509 nm? Express your answer in eV (electron-volts).

1. A plane wave in air is incident normally upon the surface of a lossless, nonmagnetic dielectric medium with relative electrical permittivity of 25 at z=0. Incident E field has an amplitude of 10 V/m polarized in +x direction and is of frequency 1 Ghz. Give the total E-field Phasor expression in air. 2. For the problem (1), determine the average power density of the reflected wave, and that of the transmitted wave. 3. Define and explain standing wave ratio. (Give a verbal description and the associated expressions) 4. For the problem (1), sketch the E-field wave pattern (Amplitude versus distance from the boundary) in air medium, indicating all critical vales and compute the standing wave ratio in the medium.

Refractive index of water at 283K is 1.34 for radiation of wavelength 580 nm. What is the polarizability of the molecule?