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light and sight in focus
Transcript of light and sight in focus
diffuse reflection other kind of reflection;
diffuse reflection an explanation Opaque materials can have regular and irregular surfaces. When regular, the direction of the reflected rays will be all the same. This is called regular reflection. When irregular, the direction of the reflected rays will all be different. This is called diffuse reflection. Even though the rays of incidence all point in the same direction, the rays of reflection will point in a different direction due to the bumpy surface, which means that the normal will everywhere still be 90 degrees with the surface, but will change because of the surface.
Incoming parallel rays bounce off the bumpy surface of the material and are scattered. refraction when rays of light reach a boundary of a different transparent material, they travel through it, but change direction. this is refraction. when doing an refraction experiment,
it should look like this. inside the rectangular block, the rays of light go in a different direction than the light rays outside the block. The Descartes-Snell law is the law in which can be calculated the refractive index. The refractive index of a medium is the relationship between the velocity of light in a vacuum and the velocity of light in that medium. It can be calculated using this formula: sin i =the refractive index or n
sin r Descartes-Snell law lenses lenses are curved transparent objects, that refract light, in a predictable way. there are two types of lenses: concave and convex lenses. these lenses are also split up in three different lenses: bioconvex or -cave, piano convex or -cave and converging or diverging meniscus convex lenses are converging lenses in which the parallel light rays come together.
concave lenses are diverging lenses where the parallel light rays go away from each other. eyes when light enters the eye...
1) ...the light goes through the transparent cornea.
2) ...the iris changes depending on how bright it is outside the eye.
3) ...the lens refracts the light. the lens of the human eye is a convex lens so the image is made smaller and now upside down on the retina.
4) ... the ciliary muscles can slightly change the shape of the lens to improve the image on the retina.
5) ...via rods and cones that are inside the retina and fovea, which actually is the spot of the middle of the lens but projected on the retina, the images are transferred to the optic nerve, which then transfers it to the brain, where the the image is turned the right way and the person is now able to see. the pupil the pupil is the black hole in the centre of the iris through which light enters the eye. vitreous humour transparent jelly stuff in the middle of the eye. blind spot the spot in the retina where the optic nerve connects with which no light can be detected. rods 120 million spread over the whole retina. used when very little light is available to see things. cones cones take care of the precision of the image and also of the colour. these can only be found in the fovea. there are three types of cones; red, green and blue. colour colour colour primary colours of light secondary colours of light complementary colours of light secondary + primary = white vision impairment colour blindness cones do not function properly.
person cannot detect (proper) difference between certain colours or cannot see some colours as bright as others.
there is no correction possible. myopia also known as shortsightedness
or nearsightedness eyeball too long.
image focused in front of the retina,
instead of on it.
can be corrected with a bioconcave lens. hypermetropia also known as longsightedness
or farsightedness Eyeball too short. Image focused behind the retina instead of on it. Can be corrected with a bioconvex lens in front of the original lens. Astigmatism lens is egg-shaped rather then spherical.
the lens has two different focal point;
one for both the horizontal and vertical part of the image.
can be corrected with a lens with a cilindercomponent. cateracts cloudiness in lens which, when left untreated, can cause blindness can be caused by:
injury to the eye
medications such as steroids
various chronic eye diseases
long-term, unprotected exposure to sunlight can be corrected with surgery trachoma caused by bacterium chlamydia trachomatis around 80 million people are affected. it is transferred between people by little flies (musca sorbens) that drink the moisture from the eyes. the inside of the eyelid becomes so scarred that it turns on itself. then the eyelashes start rubbing the cornea, which makes it very itchy, so that the eye is finally unable to transmit light. trachoma cannot be corrected. river blindness caused by the black fly worm which is a blood parasite of humans infests every part of the eye except the lens. the eyes become red and swollen, start to bleed and eventually the person becomes blind. about half a million people are affected with river blindness can be treated with a drug ivermectin the end!