5.1 reflection

7/31/2019 5.1 Reflection

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What Is Light?

In our todays lesson

1) Properties of light

2) Reflection - Mirrors


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Properties of Light

Light travels in straight lines:

Laser


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Light travels much faster than sound. For example:

1) Thunder and lightningstart at the same time,but we will see the

lightning first.

2) When a starting pistol

is fired we see the smokefirst and then hear thebang.


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Light travels VERY FAST about

300,000 kilometers per second or186,000 miles per second.

At this speed lightcould travel theequivalent of 8 timesaround the world in

one second!


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Light can create shadows

Shadows are places where light is blocked:

Rays of light


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Light travels in waves

A wave is a disturbance that transfersenergy from place to place.

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What characteristics do lightwaves have?

Light waves are like other kinds of waves.They have crests, troughs, wavelength,

frequency and speed. However, light wavesare electromagnetic! Light waves have acomponent that is electric and magnetic!!




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We see things because they

reflect light into our eyes! Thisis literally the only way we get tosee things! ALL objects we see

either create light or reflectlight!!

Homework


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Properties of Light summary

1) Light travels in straight lines and is a form ofenergy

2) Light travels much faster (a million times faster!)

than sound3) We see things because they reflect light into our

eyes4) Shadows are formed when light is blocked by an

object5) Visible light is only a small part of theelectromagnetic spectrum; the other parts areinvisible to the human eye but not necessarily theeyes of other animals.


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Part 2 - Reflection and

Mirrors


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Regular vs. Diffuse Reflection

Smooth, shiny surfaceshave a regularreflection:

Rough, dull surfaces havea diffuse reflection.

Diffuse reflectionis whenlight is scattered indifferent directions


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Using mirrors

Two examples:

1) A periscope

2) A car headlight


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Types of Mirrors: Plane, Concave, Convex



Plane mirrors are flat and make virtualimages. The images is virtual because thelight rays do not come from the image, theyonly appearto

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Concave Mirrors are curved inward - justremember, you go in to a cave, and in to a

concave mirror!

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The mirage box on Mr. Ss desk ismade of two concave mirrors.Images of concave mirrors can bevirtual or real!

VirtualimagesReal

image


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Convex mirrors are mirrors that curve outward

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Convex mirrors are used forsecurity purposes, in cars etc.They allow us to see a wideview. The images they make

are virtual


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Part 2 - Reflection andMirrors

Reflection from a mirror:

Incident ray

Normal

Reflected ray

Angle ofincidence

Angle ofreflection

Mirror


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The Law of Reflection

Angle of incidence = Angle of reflection

In other words, light gets reflected from a surface at

____ _____ angle it hits it.

Thesame !!!

5.1 reflection

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