Optics

dispersion Shorter wavelengths refract more than longer wavelengths – Violet light bent the most Color

The color of any object depends on what its made of and the color of light that strikes the object In sunlight a red car looks red because the red light is reflected from the paint and the other colors are absorbed If you shined green light on a red car there is no red light to be reflected so it looks black Color of object

Color of an object

Primary colors – can be combined in various combinations to produce all possible colors – Red – Yellow – Blue Mixing colors of light

What happens if red and blue light strike a white surface? both colors are reflected and mix together to create magenta Any two primary colors that are mixed together form a secondary color Mixing colors of light

Pigment- a material that absorbs some colors of light and reflects others – Natural pigments – clay, plants, minerals – synthetic pigments- man made Primary colors of pigments are magenta yellow cyan Mixing Pigments

Any two pigments that are mixed together and make black are called complimentary colors of pigments

Luminous- objects that give off their own light – All light sources are considered to be luminous – incandescent – Fluorescent – laser – neon – Tungsten-halogen – Sodium vapor bulbs Sources of Light

Mirrors

Optics- study how mirrors and lenses form images Ray diagram – shows how rays change direction Optics

Law of Reflection – States that the angle of reflection is equal to the angle of incidence Law of Reflection

Always produce a virtual image – copy of an object formed at the location from which the light rays appear to come Plane Mirror

Concave and convex mirrors

Concave Mirror Gcsescience.com

Concave mirror The curvature of the reflecting surface cause the light rays to come together The point where the light rays meet is called the focal point Real image- a copy of an object formed at the point where light rays actually meet

Concave mirror Concave mirrors can form virtual or real images – The type of image formed is dependent on where the object is in relationship to the mirror

Real ImageVirtual image Object is farther from the mirror than the focal point Reflected rays meet in front of the mirror object is closer to the mirror than the focal point reflected rays appear to come from behind the mirror

When an object is at the center of curvature of a spherical concave mirror a real image is formed that is inverted and the same size as the object.

Convex Mirror Convex mirrors cause light to scatter and only produce virtual images The image produced by a convex mirror is always smaller than the actual object and allows a wide angle view

Convex mirror

Convex Mirror

Lenses

Index of Refraction When light enters a new medium it refracts Index of refraction- ratio of the speed of light in a vacuum to the speed of light in the material

Index of Refraction A material with a low index of refraction (near 1) slows down light very little and will refract the light very little

Index of refraction Luster- the amount of light that strikes a gemstone and is reflected Brilliance – the amount of light that is passed through the gem Material Index of Refraction Luster Diamond % Ruby % Sapphire % Emerald %

Concave Lenses Concave lenses always cause the light rays to spread out and can only form virtual images The image is always smaller Used in the viewfinder in cameras and with mirrors in telescopes

Convex lenses Form real or virtual images depending on how far the object is from the lens As the rays pass through each one is refracted Causes parallel rays to converge and meet at a focal point

Convex lenses

Total Internal Reflection Total internal reflection is the complete reflection of a light ray back to its original medium – Critical angle – the angle of incidence that produces an angle of refraction of 90 degrees – Materials that have small critical angles are likely to cause most of the light entering them to be totally internally reflected

Fiber Optics how fiber optics work

Optical Instruments Telescopes – Reflecting telescope- uses a large concave mirror to focus incoming light rays

Optical Instruments Refracting telescope – uses a series of lenses to focus light from distant objects

Optical Instruments Cameras Microscopes