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Light

Light. Refraction and the Eye. Refraction. Refraction is the bending of light when it moves from one medium to another. When it travels from one medium to a thicker medium it slows down. When it travels from one medium to a less dense medium it speeds up. Lens.

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Light

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  1. Light Refraction and the Eye

  2. Refraction • Refraction is the bending of light when it moves from one medium to another. • When it travels from one medium to a thicker medium it slows down. • When it travels from one medium to a less dense medium it speeds up.

  3. Lens • These are thick pieces of transparent materials. • When light passes through them it refracts. • There are two types of lens: convex and concave. • A convex lens converges light. • A concave lens diverges light.

  4. Uses of lens • The eye • Cameras • Telescopes • Periscopes • Microscopes • Kaleidoscopes • Projectors

  5. Image from a lens • The image formed by a lens is called a real image. • It is inverted (upside down). • It is usually smaller. • It can be shown on a screen.

  6. Dispersion • Light that comes from the sun is called white light. It is made up of seven colours combined. • The seven colours are ROY G BIV. • Whenever sunlight or white light passes through a special lens called a prism it refracts • When white light refracts through a prism it splits into the seven colours. This is called dispersion • This is how a rainbow is formed.

  7. How do we see colours? • All materials absorb light. • However they also reflect light. • Remember white light is made up of seven colours. • We see colours when materials absorb the white light and then only reflect one of the seven colours back to you.

  8. The Eye- an organ that allows us to perceive light. • The parts of the eye are: • Pupil • Retina • Cornea • Ciliary muscles • Lens • Iris • Fovea • Aqueous humor • Vitreous humor • Optic nerve

  9. How the eye works. • Light enters through the cornea, passes through the pupil, refracts through the lens and forms an image on the retina. • This image is then sent to the brain through the optic nerve.

  10. The eye is similar to a camera • The retina is just like the film. • The eye’s lens I just like a camera’s lens. • The ciliary muscles are like focusing your camera. • The iris is just like the shutter. • The pupil is just like an aperture.

  11. Defects of the eye. • Two common eye defects are: • Short sight –A person can only see near. The image is formed inside in the middle of the eye. A person has to use concave lens. • Far sight – A person can only see far. The image is formed outside in the back of the eye. A person has to use a convex lens.

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