9. Most of the bending of light in the eye is done at the air-cornea interface. By what angle (Ocornea) is the beam of light shown in Figure deviated as it passes from air to the cornea if the incident angle is O; = 23.6°? The refractive index of air is nair = 1.00, the refractive index of the cornea is ncornea = 1.38. Explain why Ocornea< O;? Aqueous humour n= 1.34 Air n= 1.00 Vitreous humour n= 1,34 Cornea n= 1.38 Perpehdicutar to comea Pependicular to comea Lens n= 1.39 to 1.41 Eye_optical_systems.pdf OPTICS Eye optical system 1. Optical power of the cornea: Fcornea = F1 + F2 = n2-n1 Пз-пz Ciliary fibers R1 R2 F1 - optical power of the cornea front surface, D; F, - optical power of the cornea back surface, D; R, radius of curvature of the cornea front surface, m; Iris Vitreous humor Cornea Lens R, - radius of curvature of the cornea back surface, Fovea m; n, - ambient refraction index (for air n, = 1 and for water n, = 1.33); n2 – cornea refraction index; n3 - aqueous humour refraction index. 2. Optical power of the crystalline lens: Ferystalline lens = F3 + F4 F3 - optical power of the crystalline lens front surface, D; F4 – optical power of the crystalline lens back surface, D; R3 - radius of curvature of the crystalline lens front surface, m; R4 – radius of curvature of the crystalline lens back surface, m; n3 - aqueous humour refraction index; n4 – crystalline lens refraction index; n5 – vitreous humor Aqueous humor Optic nerve Retina П4-Пз пs-ng R3 R4 Sclera refraction index. Table - Parameters for the Eye Index of Radius, mm Back Front refraction R, = 7.8 R3max =10 R3min = 6 Aqueous humour and vitreous humor Cornea R, = 7.3 n2 =1.38 Crystalline lens (Fmin) Crystalline lens (Fmax) R4max = 6 R4min = 5.5 n4 =1.4 Пз 3 n5 =1.33 3. Optical power of eye: F= Fcornea + Fcristalline lens 4. Lens equation: RI Cornea. Lens R: R3/ R4 F = -= -+ f– lens focal length (m); F – lens optical power (D); p - distance from the object to the lens or object distance (m); q – distance from the image to the lens or image distance (m). 5. Height of image on the retina: h.q H – height of image on the retina, m; h – height of object, m; q – image distance (for human eye on the average is equal to 1.5 cm), m; p – distance of the object to optical system of the eye, m. 6. Lens magnification: Н M = H– image height (m); h – object height (m), p – object distance (m); q – image distance (m). 7. Law of refraction: пysin@, = n2sinO2