Refraction of Light Refraction Refraction –Refraction occurs when light waves traveling from one medium to another with a different density bend. –The incident angle and the refracted angle are a NOT equal. –When light is traveling form a less dense medium to more dense medium the angle of incidence will be greater than the angle of refraction.

Refraction Refraction makes objects appear in different positions from where they actually are. Refraction makes objects appear in different positions from where they actually are. –These are virtual images. –Refraction due to the atmosphere is known as a mirage. Heating air near the surface of the Earth on a hot day causes the air near the ground to be less dense than the air above it and an image is created through refraction. Heating air near the surface of the Earth on a hot day causes the air near the ground to be less dense than the air above it and an image is created through refraction.

Index of Refraction Ratio of the velocity of light in different mediums and the velocity of light in a vacuum. Ratio of the velocity of light in different mediums and the velocity of light in a vacuum. n = c v n = index of refraction c = speed of light in a vacuum(3.0 x 10 8 m/s) c = speed of light in a vacuum(3.0 x 10 8 m/s) v = speed of light in the medium v = speed of light in the medium

Snell’s Law sinӨ i n i = sinӨ r n r sinӨ i n i = sinӨ r n r sin Ө i = sin of the incident angle sin Ө i = sin of the incident angle sin Ө r = sin of the angle of refraction sin Ө r = sin of the angle of refraction n i = index of refraction of the incident medium. n i = index of refraction of the incident medium. N r = index of refraction of the refractive medium. N r = index of refraction of the refractive medium.

Refraction

Reflection and Refraction

Internal Reflection Total internal reflection Total internal reflection –Occurs when light is refracted so much that it is reflected back into the medium it was traveling from originally. Critical angle Critical angle –When the angle in which light rays meet the boundaries between the two mediums is so large that the boundary acts like a mirror and reflects all of the light back into the medium. Internal reflection is used in fiber optic cables. Internal reflection is used in fiber optic cables.

Total Internal Reflection

Lenses A curved piece of glass or plastic that changes the direction of light waves. A curved piece of glass or plastic that changes the direction of light waves. –Light is refracted when it enters glass and then again when it leaves the glass. –Converging lenses Bend light inward and focus light Bend light inward and focus light Create virtual and real images Create virtual and real images Also called convex lenses Also called convex lenses –Diverging lenses Bend light outward Bend light outward Create virtual images only Create virtual images only Also called concave lenses Also called concave lenses

Convex and Concave Lenses

Concave and Convex Lenses

Convex Lens Application Magnification Magnification –When the image is a different size from actual object. Microscopes Microscopes Telescopes Telescopes Lens of the Eye Lens of the Eye Glasses or contact lenses Glasses or contact lenses Cameras Cameras

Near Sighted and Far Sighted Near sightedness Near sightedness –Occurs when the eyeball is too long causing the image to be to far in front of the retina. Diverging lenses move the image back so that the image appears on the retina. Diverging lenses move the image back so that the image appears on the retina. Far sightedness Far sightedness –Occurs when the eyeball is to short and the image appears to far behind the retina. –Convex lenses move the image up

Anatomy of the Human Eye

The Eye Uses a Convex Lens

Nearsightedness

Diverging Lenses Correct Nearsightedness

Farsightedness

Converging Lenses Correct Farsightedness

Dispersion and Prisms Dispersion Dispersion –When light is refracted in such a way that it separates light into its individual color components. –Prisms are triangular pieces of glass that bend light. The angled surface causes the difference wavelengths of light to separate because they bend at different angles. The angled surface causes the difference wavelengths of light to separate because they bend at different angles. Water droplets act like prisms and create rainbows. Water droplets act like prisms and create rainbows.

Dispersion Of Light Through a Prism

Raindrops Act Like Tiny Prisms

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