Resource Guide 1 Light

8/7/2019 Resource Guide 1 Light

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ALL ABOUT

LIGHT!!

A

A resource guide forteachers and students

By Michelle Krel

3787549


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Contents

ALL ABOUT LIGHT

WHAT IS LIGHT? Page 3

ELECTROMAGNETIC SPECTRUM Page 4

COLOUR Page 5

REFLECTION AND REFRACTION Page 7

LENSES Page 8

ATOMS Page 9-10

OPTICAL ILLUSIONS Page 11

EXPERIMENTS INVOLVING LIGHT (4) Page 12-17

ACTIVITES (word search, fill the blanks etc.) Page 19-21

ACTIVITY ANSWERS Page 22-23

GLOSSARY Page 24-26

REFERENCES Page 27


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What is LIGHT!! ?

Light must have the following

3 things-

- Source

- Object

- Detector

A Source is where the light is

coming from e.g. the Sun, a

light bulb, a candle flame etc

An Object is something that

the light reflects off e.g. a

book, a person etc. (Keep in

mind that sometimes the

Object can also be the lightsource).

And the Detector is our EYE.

Light is very important for our existence on Earth. Without light we wouldnt have plants,

therefore no crops would grow for people or for animals. We would have no heat generated

from the sun therefore it would be a frozen, barren world. So what is light exactly?

FunFacts!!- Our major source of light is the SUN

- Light travels faster than sound

- Light travels 300,000 kilometres per second!!

- We see things because they reflect into our eyes- There are TWO types of light- Luminous- objects

that emit their own light (sun) and Non- luminous-

object that does not emit light (the moon)

- Light can pass through something that istransparent (like a window), can slightly pass

through something that is translucent (a frosted

window or a jelly fish), but cannot pass through

something that is opaque (like a brick wall).


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LIGHT!! is known as having Wave-Particle Duality.

As stated by K. Spring et al, the exact nature of visible

light is a mystery that has puzzled man for centuries. It

was once said that every visible object emits a steady

stream of particles however it has also been said that

light travels in a manner of waves similar to those in the

ocean.

Electromagnetic Spectrum

This is all the different wavelengths of electromagnetic radiation including radio waves, light

waves, x-ray waves etc. The Visible light (light waves) covers the range of wavelengths from

400 - 700 nm.

Gamma Radiation- deadly high energy

given out by the sun and other stars

X-rays- high energy used in x-ray

equipment

Ultraviolet rays- invisible sunlight energy

waves that cause the skin to tan

Visible Light- the basic colours of light

emitted by the sun and visible to the eye-

colours of the spectrum- ROYGBIV

Infrared rays- rays of heat energy- felt by our nervous systems

Radio waves- microwaves, radio energy & TVs

Waves

A wavelength is the distance between two troughs or two crests. The frequency is the number of

wavelengths that pass through a given point in one second. The speed of the wavelength equals

the frequency times the wavelength. The longer the wavelength = the less energy. The higher

the frequency = the shorter the wavelength. The lower the frequency = the longer the

wavelength. Amplitude is a measure of how much energy the wave has.


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Colour

Colour is only possible because of light. Visible light is made up of all different colours. These

different colours of light are seen when we see a rainbow. Red, Green, and Blue are the primarycolours. When we look at the rainbow we see all the colours of the light spectrum. These

colours are RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO and VIOLET. To remember

these colours there are a number of ways to make it easier- ROY-G-BIV is the most common

acronym.

As stated in the NASAs Optics educational guide to see the colours that make up white light

(sunlight) Sir Isaac Newton used a prism. The light passed through one side of the prism and

out the other end shone the visible spectrum broken down into the colours of the rainbow-

ROYGBIV.

The colour of an object is seen because the object reflects, absorbs and transmits one or more

colours that make up light.

The primary colours of light are different to those of paint. You may know from doing art at

school that the primary colours of paint are- blue, red and yellow. But in the form of light, the

primary colours are Red, Green and Blue.


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When we add colours together we get different colours.

Red + Blue = Magenta

Blue + Green = Cyan

Red + Green = Yellow.

By adding ALL the primary colours together you get what is known as White light. Below is a

diagram to help you understand.


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Reflection and Refraction

Reflection involves two rays- incoming ray (incident ray) and an outgoing ray (reflected ray). If

you draw a line perpendicular to a flat surface, this line is referred to as the normal. The Law

of Reflection (Snells Law) states the angle of incidence equals the angle of reflection.

Reflection from a smooth, mirror-like surface is known as specular. If the surface is rough, the

rays of light are reflected in many directions; the angles of incidence and reflection are still

equal but appear scattered. This is known as diffuse reflection.

Refraction is when light ray changes mediums. The speed of light changes when it enters a

different medium, e.g. light travelling through air then through water is an example of refraction

due to the different mediums. In most cases the direction of light changes, giving the illusion

that the light is bending. The different densities will cause the ray to slow down or speed up.When light enters a denser medium (light travels slower), the ray bends towards the normal,

when the light enters a rarer medium (light travels faster) it is bent away from the normal.

FAST SLOW bends towards normal

SLOW FAST bends away from the normal


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Lenses

A Lens is a transparent material (such as glass) that either has one flat surface and a curved

surface, or two curved surfaces.

Lenses are able to form magnified or reduced images, or to concentrate or spread light rays.

They are used as an aid for defective sight in the form of glasses and contact lenses and in

optical instruments such as microscopes, telescopes and cameras.

Have you ever looked at yourself in a spoon? Have you noticed that on one side of the spoon

you look upside down and on the other you look quite wide? This has got to do with the shape.

There are two basic types- CONCAVE and CONVEX.

Concave

- The surface curves inwards

- The lens causes light rays to spread apart or diverge- And a mirror causes light rays to meet or converge- this is why in a spoon you look upside

down

- Is thinner in the middle

Convex

- The surface curves outwards

- The lens caused light rays to meet or converge

- And a mirror causes light rays to spread apart or diverge, that is why you look wider on the

other side of the spoon- Is thicker in the middle


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Light and Atoms

All matter is made up of Atoms, they are the building blocks. The atom contains a nucleus- this

contains a positive charge. Surrounding the nucleus is electrons- these are negatively charged

and are very small.

Energy- comes in two forms- heat and light. Light is a form of electromagnetic energy and is

made up of different waves that could be described or differentiated based on their wavelength,

and their frequency. This can also determine their energy levels.

Atoms emit light (expel/give off) by reflecting light. Atoms take in the suns rays and absorb

them. Darker colours (blue, red and black) absorb more of the suns rays and lighter colours

(yellow, white and orange) reflect more of the suns light rays.

Photoluminescence talks about- light emission that is due to something absorbing heat energy,

Electroluminescence talks about- production of gases from electron discharge

Thermo luminescence talks about- light emission due to slight heating

Triboluminescence talks about- light emission due to friction

Crystlloluminescence talks about- light emission due to crystillisation

Chemiluminescence talks about light emission due to a chemical process

When an Atom is given extra energy- such as being heated by flames, or absorbing a photon

(which is a bundle of electromagnetic energy) the electrons gain energy. This is known as an

excited state. Electronsdont stay excited for very long, and soon return to their ground

state- by releasing THE SAME amount of energy they first absorbed in the first place to

become excited. Therefore whatever they take in- is what is released to return to normal.

The following diagram explanation should help in understanding atoms and the energy that is

absorbed and emitted.


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Optical Illusions - FUN


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EXPERIMENTS

EXPERIMENT 1

Making a Rainbow Spinner

Materials

Pencil White cardboard

Scissors a ruler

Glue Coloured pencils/texta/crayons

String (optional) Hole punch (optional)

Glass (to trace)

Instructions

1- Use the glass to trace 2 circles on thecardboard, and cut them out

2- Use the ruler to divide the circles into 7

even sections

3- Colour these sections in using Red,

Orange, Yellow, Green, Blue and Indigo and

Violet to simulate the colour spectrum

4- Glue both circles together so the colours

can be seen on both sides

5- Carefully make 2 small holes (1cm apart)around the middle of the circle and thread

the string evenly through the holes

6- Make a circle motion with your hands so

you flick the spinner around until the string

is twisted

7- Stop the circular motion and pull your

hands apart and back this will cause the

spinner to spin very quicklyAs an alternative to step 5

- You can poke a pencil through the middle of the

circle, making sure the pencil is evenly through.

- Put sticky tape on either side of the pencil to

secure its current position

- Hold the pencil in the palms of both hands and

move your hands back and forth (this moves the

pencil and then coloured spinner too)

- Increase the movement of your hands to make the

spinner spin fast and the colours will then blend.

Observations- The colours blend when spun fast enough and they make the colour white!! But why?

- When the spinner spins very fast the brain cannot separate each colour, so we see a mixture of

all the colours drawn and this is white.

- The spinner may look grey but this is because the colours are not pure.


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- Observe the pattern on the spinning circle. What do you see?

- What colours do you see?

- Did the colours seem to mix and become other colours?

Make a spectroscope with only 3 colours.

- How can you make green? Orange? Brown?

- Try to make other colours. Keep experimenting with your 3 colours

Additional Activities Show diffraction Grating by using a computer screen that is on, and a

grate. Move the grate to see the light coming from the computer that is behind the grate, then

change the grate vertical to see black. This is due to diffraction and that the waves cannot pass

the grate to get to the eye because they are not the right shape to pass through.

Place an empty glass and/or water bottle in front and play with the angles of the grate to see

colours.


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EXPERIMENT 2

A Spectroscope

A spectroscope is a device that lets us find out what things are made of. Its used to measure

various properties of light waves. It can measure the intensity of light, its wave length, or its

polarisation. It works by taking light in, and splitting it up into its component colours.

Different elements make differentcolours when they glow. The

spectroscope spreads out the colours of

light and we can identify the elements

by the bright lines we see in the

spectroscope.

From the energy that is broken down

into its colours, we then can plot the

colours on the light spectrum.

Materials

Glue Gun

CD

Toilet Roll- Just the cardboard from the

middle (not the whole roll!!)

Black cardboard

Scissors

Pen/Pencil

Instructions

1- Cut a circle of the CD, using the toilet roll

as a stencil

2 - Cut the circle out

3 - Glue the CD circle cut out to one of the

toilet roll

4 - Cut two squares out of the black

cardboard

5 - Glue down the black cardboard pieces,

leaving a small gap between them (keeping

in mind the smaller the gap, the better the

experiment will turn out)

6 - Bring the spectroscope to your eye, look

through the CD end, and record the colours

you see.


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Observations

- Look into the spectroscope and describe what you see

- Try different light sources. DONT AIM THIS SPECTROSCOPE TOWARDS THE SUN. Yo

look at a reflection from a white piece of paper

- Observe the colours. Start with the first colour on the left and list them in the table (below) in t

order that you see them- Does each light source produce the same group of colours or spectrum?

Light Source Colours


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EXPERIMENT 3

A Laser Course using mini-mirrors

A Laser cannot bend, however they can be reflect.

Mirrors reflect light and the type of mirror can

depend on the reflection.

The mirror shape depends on the reflection. If themirror is CONCAVE- light is made to converge

(narrow) and the reflection with be inverted. If the

mirror is CONVEX- light is diverged (spread out),

just like looking at yourself in a spoon.

Materials

A3 sheet of white paper

Handheld Laser

Mini-mirrors

Pencil/Pen to mark positions of the mirrors

Patience as this may take a little while to get

right

Instructions

1- Find the designated Start and Finish

zone for the laser

2- Put the laser on the Start zone

3- Work around the A3 piece of paper using

the mirrors to reflect the laser light until it

reaches the Finish zone

4- Mirrors can be moved back and forth and

on different angle to get optimum result

5- Mark where the mirrors are on the piece

of paper

6- Finish with 6 different courses to reach

the Finish zone.


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Observations

- The laser angle of incidence is equal to the laser angle of reflection. (This means the angle that

the laser hits a flat mirror at, will be equal to the angle it gets reflected)

- Record the angles of reflection from the flat mini-mirrors used in the course

EXPERIMENT 4

Laser LightBending with Water

This experiment displays the Refraction of

light. This is essentially the bending of a

wave when is enters a medium where its

speed is different.

Fast Slow medium bends the light towards

the normal boundarySlow Fast medium bends the light away

from the normal boundary

Materials

Laser

Bottle of water with small puncture from the bottom

Container to catch the water pouring out of the bottle

Instructions

1- Use a skewer to make a puncture (hole) in

the bottle about 8cm from the base/ from

the bottom.

2- Fill of the bottle with water, making

sure to cover the hole, either with some tape,

blu tack or your finger

3- Set the laser on some block to be in exact

same line as the hole (when the laser is on, it

must be shining straight through the hole or

this experiment will not work)

4- Uncover the hole and watch the water

spill out of the hole and see the laser

following the water and bending with the

stream!

Observations

- The laser light follows the stream of water all the way down and seems to be bending!!

- A laser light is trapped inside the stream of water by total internal reflection.

- The laser bounces of the particles in the water and reflects and then bounces off another


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particle and reflects; therefore it cannot get out of the stream of water and continues to bounce

of particles all the way down the stream of water giving the effect that the laser light is bending.

Possible Questions-

Q- Why is the sky blue?

A- The sky is blue due to scattering. As light moves through the atmosphere, most of the longer wavelengthspass straight through. (This being red, orange and yellow). However the shorter wavelength light is absorbed by

gas molecules, this is then radiated in different directions and scattered around the sky.

Q- What is a photon?

A- A photon is a separate bundle or electromagnetic energy. They are always in motion and in a vacuum havea constant speed of light to all observers. They also can be destroyed/created when radiation is absorbed/emitted

Q- What causes a bubble to have colours in it?

A- Light waves become trapped within the bubble solution and bounce around in the bubble. When a lightwave hits the surface of the bubble, part of the light is reflected back to the viewers eye and it is also reflected

within the bubble itself. When the bubble wall gets thinner, due to a weak solution of gravity, the waves start to

cancel each other out and the bubble becomes nearly invisible.

Q- What colours make white light?

A- Primary colours that make white light are Red, Green and Blue. However all colours of the spectrum canmake white, if at the right frequencies

Q- Why do we get burnt?

A- Due to the high amount of Ultra-Violet rays from the sun makes us sun burnt

Q- How do I remember the colours of the rainbow?

A- With the acronym- ROY-G-BIV- Stands for Red, Orange, Yellow, Green, Blue, Indigo and Violet

Q- Why when Im wearing black do I get hot but not when I wear white?

A- Because White reflects all colours but black absorbs all colours and also their energy. Thats why in

summer you should wear white.


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ACTIVITIES

FILL IN THE BLANKS1. Light cannot bend around objects. It travels in a ........................ line only.

2. Shadows form when objects block light. These objects are..............

3. Objects that let light pass through them are called.................

4. We see objects because light rays enter our...........after bouncing off rough surfaces.

5. Light cannot ............... around a corner, but it can be reflected.

6. Light is reflected at .......... angles from a mirror.

7. Mirrors show images that are....................

8. Refraction is when waves ............................ or slow down due to travelling in a different

medium.

9. Light rays are slowed down by water and are .............., making it look odd.

10. A cars side mirror is an example of .................

11. Photoluminescence is about light emission due to ......................... of light energy

Straight Opaque Transparent Eyes Bend Equal

Back-to-front Speed-up Bent Convex Absorption


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TRUE OR FALSE

The SUN is a light source TRUE FALSE

A Candle is a light source TRUE FALSE

A computer screen is a light source TRUE FALSE

A light bulb is a light source TRUE FALSE

The MOON is a light source TRUE FALSE

Does light travel is straight lines? TRUE FALSE

Light hits an object and bounces off, this is a reflection TRUE FALSE

Dull objects reflect MORE light than bright objects TRUE FALSE

Shiny objects reflect MORE light than rough objects TRUE FALSE

Shadows are formed when an object doesnt block light TRUE FALSE

The closer an object is to a light source the smaller is it TRUE FALSE

A mirror that is curved outwards is known as Concave TRUE FALSE

When atoms get excited this is known as ground state TRUE FALSE


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Word SearchLight

light reflection shadow beam source

mirror refraction sun candle transparent

translucent opaque waves luminous

s s f e C h u j s u n h y b n k

l u e s D r t c x d e f h u j k

p o m n B h f d o p a q u e d e

c n t e G u j h t f c d g o e c

f i e i T u y h j I u o l s p y

t m l y G r e f l e c t i o n n

n u m s J h a t f r d e I u n k

e l j h B h g n r d c x z r g t

r b e a M g r d s w s r f c g p

a o k d U h m t f l e w a e g e

p c a o H n j i t f u u h y b g

s m n w A v e s r w a c f r u y

n p l k M n b a g r c t e e s d

a w q a T r c h u j o m k n l mr r g v H t k l f r w r e a t e

t t h b I u k l p o n h y j k l

h e d o S g t f r d h j b v r e

d I n p L j u b h e l d n a c s


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ACTIVITY Answers

FILL IN THE BLANKS1. Light cannot bend around objects. It travels in a STRAIGHT line only.

2. Shadows form when objects block light. These objects are OPAQUE

3. Objects that let light pass through them are called TRANSPARENT

4. We see objects because light rays enter our EYES after bouncing off rough surfaces

5. Light cannot BEND around a corner, but it can be reflected6. Light is reflected at EQUAL angles from a mirror

7. Mirrors show images that are BACK-TO-FRONT

8. Refraction is when waves SPEED UP or slow down due to travelling in a different medium.

9. Light rays are slowed down by water and are BENT, making it look odd.

10. A cars side mirror is an example ofCONVEX

11. Photoluminescence is about light emission due to ABSORPTION of light energy

TRUE OR FALSE

The SUN is a light source TRUE FALSE

A Candle is a light source TRUE FALSE

A computer screen is a light source TRUE FALSE

A light bulb is a light source TRUE FALSE

The MOON is a light source TRUE FALSE

Does light travel is straight lines? TRUE FALSE

Light hits an object and bounces off, this is a reflection TRUE FALSE

Dull objects reflect MORE light than bright objects TRUE FALSE

Shiny objects reflect MORE light than rough objects TRUE FALSE

Shadows are formed when an object doesnt block light TRUE FALSE

The closer an object is to a light source the smaller is it TRUE FALSE

A mirror that is curved outwards is known as Concave TRUE FALSE

When atoms get excited this is known as ground state TRUE FALSE


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Word Search

Light

mirror

reflection

shadow

beam

source

refraction

sun

candle

transparent

translucent

opaque

waves

luminous

s s f e c h u j s u n h y b n k

l u e s d r t c x d e f h u j k

p o m n b h f d o p a q u e d e

c n t e g u j h t f c d g o e c

f i e i t u y h j I u o l s p y

t m l y g r e f l e c t i o n nn u m s j h a t f r d e I u n k

e l j h b h g n r d c x z r g t

r b e a m g r d s w s r f c g p

a o k d u h m t f l e w a e g e

p c a o h n j i t f u u h y b g

s m n w a v e s r w a c f r u y

n p l k m n b a g r c t e e s d

a w q a t r c h u j o M k n l m

r r g v h t k l f r w R e a t e

t t h b i u k l p o n H y j k l

h e d o s g t f r d h J b v r e

d I n p l j u b h e l D n a c s


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GLOSSARY

Absorb

Suck up/ Take in

Amplitude

How much energy the wave has

Atom

Basic unit of matter, nucleus is central, surrounded by a cloud of negatively charged electrons

Concave

curving inwards

Converge

Come together

Convex

Curving or bulging outwards

Detector

Our eye, detects the light, organises, imports information that we are seeing to our brain

Diffuse reflection

When the surface is rough and reflected rays go in many directions

Diverge

Move/draw apart, extend in different directions

Electromagnetic Spectrum

Shows us different wavelengths from Radio Gamma Rays

Frequency

Number of wavelengths that pass through in one second

Incident Ray

Incoming ray


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Lens

A transparent optical device used to converge or diverge transmitted light and to form images

Light

The natural agent that stimulates sight and makes things visible- electromagnetic radiation is

from about 390 to 740nm in wavelength

Luminous

Objects that emit their own light e.g. the Sun

Non-luminous

Objects that do not emit their own light e.g. the Moon

Normal

A line perpendicular to a surface

Object

Something that the light reflects off e.g. tree, person etc

Opaque

Light cannot pass through it (a brick wall)

ReflectionLight of image you see when light bounces off a surface, bounding a wave or ray off a surface

Reflected Ray

Outgoing ray

Refraction

When light bends due to a change in speed from one medium to another

ROY-G-BIV

Acronym to remember colours of the spectrum= Red, Orange, Yellow, Green, Blue, Indigo and

Violet

Source

Where the light originates from


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Specular

Reflection from a smooth mirror

Speed

frequency x wavelength

TranslucentLight can slightly pass through it (jelly fish, cloudy window)

Transmit

Transfer to another

Transparent

Light can pass through it (a window)

Wavelength

Distance between two troughs/crests

Wave-Particle Duality

The fact that Light travels in both Waves and Particles


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Extra Resources for Teachers

Use the National Aeronautics and Space Administration (NASA) website and

various journals on science topics

http://www.nasa.gov/home/index.html

Use the Free Games for you website regarding the science online educationalgames. These can be the base for any in class games

http://sciencegames.4you4free.com/index.html

Struggling for experiments? This website will help in all aspects around science

http://www.kids-science-experiments.com/

Fancy some Light reading?

Light Years and Time Travel: An exploration of mankinds enduring fascination

with Light By Brian Clegg may shed some light on some shady areas.

Microscopy Resource Center shows the physics and concepts to do with this topic

http://www.olympusmicro.com/index.html

REFERENCES

http://sciencegames.4you4free.com/light_optics.html

http://sci-toys.com/scitoys/scitoys/light/cd_spectroscope/spectroscope.html

My Science- Light and Optics

C. Roychoudhuri, 2008 The Nature of Light: What is a Photon? CRC Publisher

K. Spring, M. Davidson, Microscopy Resource Centre 2010

NASA Optics: Light, colour and their uses, Educational Product, Spacelink.

Documents

Resource Guide 1 Light