Post on 16-May-2015
description
Optics: lenses, mirrors, and
electromagnetic spectrum
Physics
Properties of Light
1) Light travels in straight lines2) Light travels much faster than sound3) We see things because they reflect light into
our eyes4) Shadows are formed when light is blocked by
an object
Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Visible spectrum
VisibleEach color is a different size wave.
Red the longest & violet the shortest• Emitted by– The sun and other
astronomical objects– Laser pointers– Light bulbs
• Detected by– Cameras (film or digital)– Human eyes– Plants (red light)– Telescopes
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What are sun rays?• The sun emits several kinds of electromagnetic radiation:
Visible (Vis), Infrared (IR) and Ultra Violet (UV)
Each kind is distinguished by a characteristic wavelength, frequency and energy
• Higher energy radiation can damage our skin
High Energy Low Energy
Colour• White light is not a single colour; it is made
up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism:
*Animation
The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of reflectionAngle of incidence = Angle of reflection
The same !!!
Clear vs. Diffuse Reflection
• Smooth, shiny surfaces have a clear reflection:
Rough, dull surfaces have a diffuse reflection.
Diffuse reflection is when light is scattered in different directions
Refraction• The change in direction of a wave as
is crosses the boundary between two media in which the wave travels at different speeds.
Convex lenses• Refracts parallel light rays so they come
together at a single point (convergence). • Distance from center of lens to focal point
= focal length.• The thicker the middle of the lens the
shorter the focal length.
Concave lenses
• Refracts the rays so they come apart. -Known as divergence.
• Always forms a virtual image.
• Show overhead of concave lens.