science

• An optical instrument in which reflected light is reflected again is called a periscope a periscope is a long tubular device through which a person can see objects that are out of the direct line are periscope works on the reflection of light from 2 plain mirrors arrange parallel to one another
• Kaleidoscope consists of three long narrow strips of plain mirrors inclined at 60 degree to one another forming a hollow prism and fitted into a cardboard tube
• The ability of eye to continue to see the image of an object for a very short duration even after the object has disappeared from the view is called persistence of vision
• Iris is the coloured part of the eye the iris has a hole inside its centre called pupil it controls the amount of light entering in the eye by adjusting the size of pupil
• eye lens is a convex lens it is held in position by ciliary muscles
• ciliary muscles can change the curvature of an eye lens to make it a thin according to the need
• Ratina is a screen on which image is formed in the eye lens focus the image of an object on the retina
• Optic nerve carries the image formed on retina to the brain