LIGHT Resource Guide

8/6/2019 LIGHT Resource Guide

1/25


2/25

2

CONTENTS

Intended student learning outcomes 3

Intro 4

Reflection 5

Wavelengths 9

Light Energy 12

Worksheet 1: Convex and Concave Lenses 14

Worksheet 2: Behaviour of Atoms under Light Energy 15

Glossary 16

Experiment 1: Foil Mirror 17

Experiment 2: Sunrise and Sunset 18

Experiment 3: The Colours of Light 19

Explanation of Discussion Questions

Experiments 20

Worksheets 23

Some other recommended websites 25


3/25

3

Intended student learning outcomes

This resource guide is aimed at Level 4 students It fulfils the VELS standards as

indicated inhttp://vels.vcaa.vic.edu.au/vels/science.html. It revisits

information from level 2 and 3 sciences, about light and reflections.

At the conclusion of this course, students should be able to:

Understand the ways in which the reflection of light is affected by evenand uneven surfaces. (Experiment 1: Foil Mirror)

See the connection between wavelengths and the colour of light.(Experiment 2: Sunrise and Sunset)

Recognise the different colours which result from the combination ofred, blue and green light. (Experiment 3: The Colours of Light)

Understand how differently shaped reflective or transparent surfacesmanipulate the direction of light. (Worksheet 1: Convex and Concave

Lenses)

Know how atoms behave under the influence of light energy.(Worksheet 2: Behaviour of Atoms under Light Energy)

Conceptualise how light travels in the form of wavelengths. Notice the relation between wavelength and energy of light and how

invisible light works.
http://vels.vcaa.vic.edu.au/vels/science.htmlhttp://vels.vcaa.vic.edu.au/vels/science.htmlhttp://vels.vcaa.vic.edu.au/vels/science.htmlhttp://vels.vcaa.vic.edu.au/vels/science.html


4/25

4

There are many different forms of light that we see or

use in our everyday life. This might be a light bulb, a rainbow,

the sun or forms of lights that the human eye cant see, like

ultraviolet or infrared light.

This resource guide explores the traits and amazing qualities

of light and how it works.


5/25

5

No matter what type of light we encounter, there are

particular traits which are common to all light rays. One of

these traits is the way that light moves. Just like a tennis ball

being thrown at a wall, light bounces off its obstructions. Thisis called reflection. However, light always travels in straight

lines. Its path does not curve or fall with gravity like a ball

would.

Incident light occurs when light travels from its source (e.g. a

light bulb or the sun) directly onto a surface (e.g. the ground

or an object). In order for reflection to occur, there has to

first be incident light.


6/25

6

To explore the ways in which light rays travel, you could use a

bright torch or even a laser light to investigate how these

lights behave when they are shined onto smooth and shiny

surfaces. Some materials which may be interesting toexperiment with are mirrors, windows and steam.

Hint: A dark room could make your observations clearer!

Here is a fascinating way in which reflection is used in our

everyday technology.

Can you think of any others?


7/25

7

It is not uncommon that people are long or short sighted.

This occurs because the eye does not reflect and process light

the way that it should. So how do glasses and contact lenses

correct impaired vision?

The curved shape of these lenses manipulates the path of the

light rays so that the eye can focus on an image.

Where else may you have seen some odd manipulation of

light?


8/25

8

So what is it that makes the lights direction change when it

travels through the lens? This is because when light passes

through transparent substances of different densities, for

example, glass, water or air, the speed of the light changesand therefore the direction is also affected. This action is

called Refraction.

An example of this is when you observe a spoon or a solid

object sitting in a glass of water. As the light shines into the

glass what do you see?


9/25

9

So how do so many different types of light occur? What is it

that allows light rays to shine bright or dim or coloured or

invisible? It is because of their different wavelengths.

Wavelengths are the way in which light travels, but they also

have other traits which influence how light is presented.

Here you can see that the smaller and more frequent waves

over a period of time show colours on the purple end of the

spectrum, whereas the red end of the spectrum has larger

waves over the time period.Each of these colours has adistinct wavelength. Light rays which give a particular colour

of light are called monochromatic light. This occurs when the

rays of light have wavelengths between a discrete, particular

range. For example, the rays from a green laser light would

be monochromatic with very little variance in the

wavelengths.


10/25

10

The amplitude of a wavelength determines how bright a light

is, and the frequency determines the colour and visibility of

light.

The picture above is of a prism. When a white light is at

shined at a particular angle, the prism reveals the

components of light which make up the white light. So what

does this picture show us? Well, white light is actually made

up of these seven colours. They appear in this order becausethe frequencies of the wavelengths gradually increase,

starting from the red end of the spectrum to the violet light.

The same thing occurs when a rainbow appears. Puddles,

bubbles and CDs are also able to separate white light into its

components.


11/25

11

There are some forms of light with a frequency so high that

they cannot be seen by the human eye. Some of these are

infrared light which in used in remotes to transmit

information, x rays which has enough energy to travelthrough human flesh and gamma rays which are common in

nuclear radioactive environments, capable of mutating and

damaging human tissue and cells.

Ultraviolet rays are a form of light which the sun emits onto

the Earth. Its frequency is higher than that of the violet lightat the end of the spectrum, below 400 nanometres. These

rays are capable of causing reactions within our skin,

resulting in burns and damage, but luckily for us, most of the

suns UV raysare blocked by the Earths atmosphere.

However, we must still protect ourselves from the UV light

which does reach our skin. To prevent sun burn or more

crucially, skin cancer, we must use sun screen and

appropriate clothing.


12/25

12

So how is light able to cause reactions in our skin and other

substances? Well, all substances are made up ofatoms.

These atoms carry energy in their electrons. Think of an

electron as a tiny planet which circles the sun (protons andneutrons) on its particular orbit. When an atom gains

excessive energy, its outermost electrons or photons can

jump to an orbit which is further away from core of the atom.

This energetic photonchanges the behaviour of the atom so

that it moves much more vigorously, and creates more

pressure in its environment as it tries to avoid its

neighbouring atoms.

For example, when a balloon filled with molecules of air is

exposed to light energy, it will expand. This is a result of thelight energy being absorbed by the atoms, causing more

movement and therefore more pressure on the walls of the

balloon. Accordingly, when light energy is removed the

atoms will lose their energy and movement will decrease, the

balloon will consequently shrink.


13/25

13

To explain what exactly how the atoms behave, we are going

to suggest that an atom is similar to a 4 year old child. When

you give a 4 year old some red cordial or light energy, the

child will get excited. He will run around like crazy, bumpinginto its surroundings and causing havoc. Eventually the child

will run out of sugar, or energy, and he will return to his

natural state. As this occurs, he will release energy in the

form of movement, heat and sweat.

When in excited state, atoms are more likely to react withother atoms to create new molecules or new substances.

This is because the movement that light energy causes in an

atom results in collisions with other atoms. The new

structure of the atom its excited photons means that other

atoms may be attracted differently to it. This means that

other atoms or may be more likely to react with this excited

atom, and therefore creating a new molecule.


14/25

14

Convex and Concave Lenses

Considering the size of the flower when looking through a straight lens:

Draw a line to connect the

lenses to the correct image

EXTENSION QUESTION: What would be

the similarities or differences between the

images portrayed by a lens and a mirror?


15/25

15

Behaviour of Atoms under Light Energy

1) Which balloon is most likely to be under light energy? :

2) Which atom is most likely to be in its excited state? :

3) Which group of atoms is most likely to be a gas under

light energy? :


16/25

16

Glossary

Amplitude: The measure of the height of

a wavelength.

Atoms: Matter which make up all

materials.These are made up of protons,

neutrons and electrons.

Concave: A curved surface in which the

centre is furthest away from the eye. This

manipulates the reflection of light.

Convex: A curved surface in which the

centre is closest to the eye. Thismanipulates the reflection of light.

Converging: This is the behaviour of light

rays which travel towards one point of

focus.

Diverging: This is the behaviour of light

rays which travel away from one point of

focus.

Electrons: The negatively charged

particles which orbit the positive centre of

an atom.

Frequency: A unit of measurement for

wavelengths.

Gamma rays: A dangerous, reactive light

ray which is generated by nuclear

explosions. It is invisible light with an

extremely small wavelength and massive

amounts of energy. Gamma rays are

known to kill living cells.

Incident light: The light which travels from

its source directly onto a surface.

Infrared light: An invisible light which

produces heat. It has a larger wavelength,

not much larger than that of red light.

Molecules: A group of bonded atoms.

Monochromatic light: Wavelengths of

one general range of frequency, which a

particular coloured light.

Photons: The outer electrons of an atom.

These are the electrons which are able to

move to outer shells when an atom gains

energy.

Pressure: The amount of force on a

surface.

Prism: Aclear triangular 3D tools which

can split a white light into its seven visible

wavelengths.

Reflection: When incident light continues

to move off a surface.

Refraction: When light moves from one

medium (air) to another medium (water),its speed changes and therefore changes

the direction of the light.

Spectrum: The different wavelengths of

light.

Ultraviolet rays: An invisible light which

can burn and damage human skin. It has a

shorter wavelength, not much shorter

than that of violet light.

Wavelengths: The way in which light

travels.

X-ray: This light allows us to see through

human flesh. Its wavelengths are short,

but have large amounts of energy. Its

wavelength is between that of Ultraviolet

light and Gamma rays.


17/25

17

Experiment 1: Foil Mirror

(from Singleton, G., 2004, 101 Cool Science Experiments, Dingley, Victoria)

Aim:

To observe how light is reflected on different surfaces.

Materials:

Aluminium foil

Scissors

Method:

1. With the scissors, cut a ruler length (30cm) sheet of aluminium foil. Make sure it is smooth!2. Look at your reflection and use some describing words to note down your observations in

the table below.

3. Without breaking it, or crushing it too tightly, scrunch the foil into a ball.4. Now, carefully flatten the ball out again.5. Look at your reflection again and use some describing words to note down your

observations.

Observations:

Smooth Foil Scrunched Foil

Discussion:

Explain the behaviour of light when it is reflected on a smooth surface. Why cant you see your reflection on an uneven surface? List three reflective objects and three non-reflected surfaces.


18/25

18

Experiment 2: Sunrise and Sunset

(from Singleton, G., 2004, 101 Cool Science Experiments, Dingley, Victoria)

Aim:

To understand why the sky changes colour during sunrise and sunset.

Materials:

1 Clear drinking glass or glass jar

cup of Water

cup of Full cream milk

1 Stirrer (e.g. paddle pop stick or

teaspoon)

1 Torch

A dark room

Method:

1. Fill the drinking glass or glass jar with the cup of water.2. With the torch shining through the glass from above, note down what colour you see (in the

Observations section).

3. Pour the cup of milk into the glass, and mix it with the teaspoon.4. In a dark room, shine the torch into the side of the glass. Note down yours observations.

Observations:

Water under the torch light:

__________________________________________________________________________________

__________________________________________________________________________________

Milk under the torch light:

__________________________________________________________________________________

__________________________________________________________________________________

Discussion:

Explain how light waves behave during a sunset or sunrise. Why is the sky blue during the day and dark during the night? Estimate the frequency of the light from the torch in the milky water.


19/25

19

Experiment 3: The Colours of Light

(from Robinson, T., 2008, The Everything Kids' Science Experiments Book : Boil Ice, Float Water,

Measure Gravity-Challenge the World Around You!, e-book, accessed 08 May 2011,

.)

Aim:

To observe how different colours combine to make white light.

Materials:

3 Torches

1 Red, 1 blue and 1 green sheet of

cellophane (big enough to cover the

light of a torch)

3 Rubber bands (big enough to fit

around torch)

A dark room with a white screen or

wall

Method:

1. Secure a sheet of cellophane to each separate torch with a rubber band, so that you have atorch shining red light, a torch shining blue light and a torch shining green light.

2. Shining these coloured lights on a white screen or wall in a dark room, observe and recordthe colour you see when you overlap the red and blue lights.

3. Observe and record the colour you see when you overlap the green and blue lights.4. Observe and record the colour you see when you overlap the green and red lights.5. Now shine all three coloured lights so that they all overlap. Observe and record the colour

you see.

Observations:

Red light + Blue light = _______________

Red light + Green light =_______________

Green light + Blue light =_______________

Red light + Blue light + Green light =_______________

Discussion:

What are the primary colours or light? What are the secondary colours of light? List 3 examples of coloured light combinations that you have seen or experienced.


20/25

20

Explanation of Discussion Questions

Experiment 1: Foil Mirror

Explain the behaviour of light when it is reflected on a smooth surface.a. When light reflects of a smooth surface, its light rays are able to reflect in the

same direction, or angle. This means that when you look in a mirror, the

reflection of the image will appear the same since the whole image is

reflected in the same general direction.

Why cant you see your reflection on an uneven surface?a. An uneven surface causes light rays to reflect in different directions so the

reflection of the image is scattered and indistinguishable.

List three reflective objects and three non-reflected surfaces.a. Reflective: window, spoon, metal, transparent liquids (water), shiny surfaces.b. Non-reflective: cloth material, table, skin, non-transparent liquids (milk).

Recommended reading:a. http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-

photography/#more-122

b. http://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.html

c. http://science.howstuffworks.com/light2.htm
http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.htmlhttp://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.htmlhttp://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.htmlhttp://science.howstuffworks.com/light2.htmhttp://science.howstuffworks.com/light2.htmhttp://science.howstuffworks.com/light2.htmhttp://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.htmlhttp://zonalandeducation.com/mstm/physics/light/rayOptics/reflection/reflection1.htmlhttp://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122


21/25

21

Experiment 2: Sunrise and Sunset

Explain how light waves behave during a sunset or sunrise.a. There are many particles in the sky, including water, debris, and gases. As

white light rays collide with these, they can behave in two different ways. If a

collision occurs with a larger molecule, such as a water droplet, the white

light will reflect off the water and will remain seen as white light. However,

smaller molecules, like dust or gases, tend to absorb some of the light. This

means that if a molecule absorbs the orange and red rays of a white light ray,

then the reflected light will also be seen as orange and red. Because the sun

is angled closer to the earths surface during sunrise and sunset, the light

makes more contact with dust and gas particles, resulting in a sky filled with

colours from the red end of the light spectrum.

Why is the sky blue during the day and dark during the night?

a. During the day, the sun is high in the sky. This angle allows light to reach theearth without must contact with dust. However, the gaseous atmosphere

does absorb and reflect shorter wavelengths resulting in a sky of blue, green

or colours of this area in the spectrum.

Estimate the frequency of the light from the torch in the milky water.a. Wavelengths should be relative in size as shown below

Recommended reading:a. http://www.ehow.com/about_5091308_sun-change-colors-sunset.htmlb. http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-

Vis/spectrum.htm
http://www.ehow.com/about_5091308_sun-change-colors-sunset.htmlhttp://www.ehow.com/about_5091308_sun-change-colors-sunset.htmlhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htmhttp://www.ehow.com/about_5091308_sun-change-colors-sunset.html


22/25

22

Experiment 3: The Colours of Light

What are the primary colours or light?o Red, blue and green

What are the secondary colours of light?o Yellow, magenta and cyan (light blue)

List 3 examples of coloured light combinations that you have seen or experienced.o Rainbow, bubbles, CDs, puddles, soapy water, oils.

Recommended reading:o http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-

photography/#more-122
http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122http://www.z-oc.com/blog/2007/08/some-physics-background-related-to-photography/#more-122


23/25

23

Behaviour of Atoms under Light Energy - EXPLANATION

1) Which balloon is most likely to be under light energy? :

B When under light energy, the atoms in the balloon absorb energy. This causes the atoms

move more vigorously and fight its surroundings for more space, causing an increase in

pressure. The balloon expands due to the increased pressure .

2) Which atom is most likely to be in its excited state? :

B When an atom is in its excited state, its outer electron leaves its natural position and

moves to an outer shell. after it has used up its extra energy, it will return to its natural

position again.

3) Which group of atoms is most likely to be a gas under light energy? :

A Gaseous atoms under light energy like to spread out in the entire area of their container.

They move erractically, resulting in collisions and allowing for atoms to bond with other

atoms or molecules


24/25

24

Convex and Concave Lenses - EXPLANATION

Considering that this is the size of the flower when looking through a straight lens:

Draw a line to connect the lenses to the correct image:


25/25

Concave and Conves Lenses EXPLANATION

What would be the similarities or differences between the images portrayed by alens and a mirror?

- Mirrors have an opposite effect to a lens when manipulating light which acurved surface. A convex lens will converge light while a convex mirror will

diverge light. A concave lens will diverge light while a concave mirror will

converge light.

See website:

http://van.physics.illinois.edu/qa/listing.php?id=1946for more information

Some other recommended websites:

http://science.hq.nasa.gov/kids/imagers/ems/index.html http://www.historyforkids.org/scienceforkids/physics/light/
http://van.physics.illinois.edu/qa/listing.php?id=1946http://van.physics.illinois.edu/qa/listing.php?id=1946http://science.hq.nasa.gov/kids/imagers/ems/index.htmlhttp://science.hq.nasa.gov/kids/imagers/ems/index.htmlhttp://www.historyforkids.org/scienceforkids/physics/light/http://www.historyforkids.org/scienceforkids/physics/light/http://www.historyforkids.org/scienceforkids/physics/light/http://science.hq.nasa.gov/kids/imagers/ems/index.htmlhttp://van.physics.illinois.edu/qa/listing.php?id=1946

Documents

LIGHT Resource Guide