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FREE ENGLISH SPEAKING COURSE

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  Learn American English  Online! This  free  website has helped students worldwide improve English grammar and vocabulary skills since 2003. There are seven levels of instruction:  blue ,  red ,  yellow ,  green ,  purple ,  orange , and  violet .  Bookmark this page now  and come back every day. New students start here:  The Blue Level  (1) is for beginning level students If you are a new student, start in the Blue Level. Lesson 1: be Lesson 2: be - negative Lesson 3: be - questions Lesson 4: nouns and pronouns Lesson 5: this that these those Lesson 6: there Lesson 7: present tense More Blue Level lessons The Blue level: review The Blue Level  test #1   /   test #2 Print: The Blue Level checklist After you finish the Blue Level, move forward to the Red Level. The Red Level  (2) is for beginning level students Lesson 1: do Lesson 2: do not Lesson 3: do and did Lesson 4: commands Lesson 5...
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Structure of human eye,,,,

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  Concepts you cannot miss #Humaneyes #RainbowFormation #VisionDefects #ScatteringOfLight #Lens #AtmosphericRefraction #Dispersion #1 Structure of human eye The working of human eye is based on refraction by a lens. Some components of human eye are: Sclerotic:  Outermost covering of the human eye from inside. It protects the eye from internal damage and is opaque. Cornea:  Outermost covering of the human eye from outside. It protects the eye from external damage and is colourless. Retina : Acts as a screen on which image is formed. It is made up of two types of cells- rods (cylindrical) and cones (conical cells).  Rods are sensitive to dim light. Cones are sensitive to bright light and responsible for colour identification. Iris : Dark-coloured muscular diaphragm with a small circular opening in the middle. It regulates the amount of light entering the eye by adjusting the size of the pupil. It provides colour to the eye. Pupil : Central circular aperture of iri...
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