TAILIEUCHUNG - text book of medical physiology (eleventh edition): phần 2

part 2 present the content: optics of vision physical principles of optics, receptor and neural function of the retina, central neurophysiology of vision, the sense of hearing, the chemical senses-taste and smell, cortical and brain stem control of motor function, contributions of the cerebellum and basal ganglia to overall motor control, cerebral cortex, intellectual functions of the brain, learning and memory physiologic anatomy of the cerebral cortex. | CHAPTER 49 The Eye I. Optics of Vision Physical Principles of Optics Before it is possible to understand the optical system of the eye the student must first be thoroughly familiar with the basic principles of optics including the physics of light refraction focusing depth of focus and so forth. A brief review of these physical principles is presented then the optics of the eye is discussed. Refraction of Light Refractive Index of a Transparent Substance. Light rays travel through air at a velocity of about 300 000 km sec but they travel much slower through transparent solids and liquids. The refractive index of a transparent substance is the ratio of the velocity of light in air to the velocity in the substance. The refractive index of air itself is . Thus if light travels through a particular type of glass at a velocity of 200 000 km sec the refractive index of this glass is 300 000 divided by 200 000 or . Refraction of Light Rays at an Interface Between Two Media with Different Refractive Indices. When light rays traveling forward in a beam as shown in Figure 49-1 strike an interface that is perpendicular to the beam the rays enter the second medium without deviating from their course. The only effect that occurs is decreased velocity of transmission and shorter wavelength as shown in the figure by the shorter distances between wave fronts. If the light rays pass through an angulated interface as shown in Figure 49-1B the rays bend if the refractive indices of the two media are different from each other. In this particular figure the light rays are leaving air which has a refractive index of and are entering a block of glass having a refractive index of . When the beam first strikes the angulated interface the lower edge of the beam enters the glass ahead of the upper edge. The wave front in the upper portion of the beam continues to travel at a velocity of 300 000 km sec while that which entered the glass travels at a velocity of 200 000 km .

• Y khoa - Dược
• Text book of medical physiology
• Optics of vision physical
• Principles of optics
• The sense of hearing
• Contributions of the cerebellum
• Intellectual functions of the brain
• Human body and control
• The cell and its functions organization
• The cell physical structure
• Membrane potentials
• Excitation of skeletal muscle