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on 8 May 2014

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Transcript of Light

Science Fiction:
With light and sound in mind what is wrong with this movie scene?
What do we know about
light already?

-made by
-made of
-travels by
-similar to
The Electromagnetic Spectrum
Why are some waves considered to be bad for you?
Light Wave Interactions
What are some wave interactions we learned from last chapter?
EM Waves are forms of radiant energy that have
electric and magnetic components.

-transverse waves created by changing electric and magnetic ______
-do not require a medium (radiant)
-fields are ______ to each other
How do electromagnetic waves help explain light?

-Light is emitted as __________
-Begins with __________
-Then __________
-they are packets of energy that can travel
like particles.

But they are...
-without mass
-shapeless and indivisible
These waves of light can travel at
__________ m/s.

Speed of light constant


880,000 times faster
than sound
What is a light year?

How would you go about calculating
one given c?
What are some other waves
that you already know of?
The electromagnetic spectrum represents the different types of waves based on ____ and ____

High frequency and low wavelength waves ______
Radio Waves
-lowest frequency
-_______ wavelength

How do these work to get the sound from point A
to point B? (use knowledge from last chapter)

-Because they are to the right of radio waves on the spectrum

How do they work?
Radar: Radio Detection and Ranging
Determines _______ using
microwave pulses.
_______ waves are emitted
from objects that are warm

-warm particles vibrate emitting
waves in the process
Partner Activity
Visible light and UV light are the next two groups
of waves that we will talk about.

-Given how frequency and wavelength have been changing as we move on, why is UV light dangerous? Describe how it might cause these negative effects and what can be done to prevent them?
Visible Light
We only see a narrow amount of EM waves
-Between 400 and 700 nanometers

-Low energy = Which color?

-High energy = which color?
Remember the order as ___________
How do we see colors?
This means that plants
UV Light
-Good for ____
-Bad for ____

400-100 nanometers
SPF-Sun Protection Factor _____________

What relationship does SPF have to the amouint of UVlight blocked?

Without Sunscreen
-______ collide with your ______
-This can cause ________ leading to cancer
X-Rays and Gamma Rays have _______
wavelengths and ______ frequency

X-rays are used for __________
-Protection _________
Gamma Rays are used for ________
The Law of Reflection

*With a smooth, flat, reflective surface*

-The angle of incidence _________
-The line that bisects the angle is the normal
How do make-up mirrors work?

Are they the same as or different from
the mirrors on cars?
We see two more interactions while driving during a foggy morning?

Are these two interactions
the exact same?
-bending of light as it _________
How can we explain light separation?
What are the two interactions seen here?
Seeing Color
Short wavelengths bend_________






Color Filters


These are either _____ or ______
By mixing all of the primary colors of light together you get ______ as a result.

HW: pg 588
1-17, 20, 21, 23
A material that _________
Primary Pigments-
3. Using what you have learned so far, describe how a glow stick works.

2-4 sentence description
Yesterday we recreated the double slit experiment that helped prove light acted as a wave.

1. If light was not a wave what might we have seen?

2. What did we see that was evidence of light acting as a wave?
7. Why do we refer to them as primary colors
of light?
Primary Colors-
Color Addition-
When printing we use cartriges that contain ___,___ and _____

To make the primary light colors we need to combine


Use a microscope or magnifying lense to determine
the pigments used. (try to determine how much)
LCD screens are only lit by white light.

4.How do they obtain so many different colors?

5. How do they obtain black (when the monitor is on)?

6. Why does the screen go black when the monitor is off?
Today you will get points for participating
in notes.

This will pay off when studying for your
next exam.

1. Answer each question during notes then they will be checked at the end to see if you
made an intelligent response

2. Receive points for thinking
Seeing Light


Types of Lights
Black Lights
Produce light and ____ when
Efficient for lighting?
Produces light when
1. electrons run into _____ atoms
2. Photons are emitted as ____ light
3. Photons are absorbed by ______ which glow
Efficient for
Like fluorescent lights but have
a filter that only removes _____

Emits ______ and UV-A
Produce light when electrons excite ______

*other gases are used to produce a variety
of colors*
Your Homework:

Take a survey of the lights at school and in your
1. Make a table that shows:

Number of incandescent
Number of florescent
Which type of lights are used most often

2. Then write down your reasoning on why these types of lights would be used in these two locations. (cost, electricity use, lighting needs, size, personal preference)

3. Your house will likely have a mixture of both types. Write down why you think florescent are used in some areas while incandescent are found in others.

Energy Consumption of Lights
Light and Mirrors
In order for you to
see an object
where does light

What happens
when light strikes
a mirror?

Plane Mirrors-
has a ___ surface

Images appear___
Drawing ray diagrams for plane mirrors
Law of Reflection:
Angle of incidence=Angle of reflection
Concave Mirrors-curved inwards it goes in like a cave)

Image is __________________________depending on
Useful for _________________________

Focal Length:

Optical Axis:
Ray diagrams for concave mirrors
Rule 1. Draw a ray from the top of the image parallel to the axis and then reflects through the focal point
Rule 2. If the object distance is > focal length, draw a line from the top of the object, through the focus and then parallel to the optical axis.
Rule 3. If the object distance < focal length, the ray is drawn from the focal point through the top of the object then reflected parallel to the axis
The point where the lines cross is where the top of the image will be.

Real image-an image through which light will pass. (in front of the mirror only)

Virtual image-
behind the
Convex Mirrors- curved outwards

Image is________________
Useful for_______________

Rules for ray diagrams
are similar
Lines that go behind
the mirror are dashed
Initial Cost
Upkeep Cost
Consumption Cost
Which luminous object to illuminate your home?
Unwritten Rule- Perform all ray diagrams with a ruler and sharp pencil
Convex and Concave Mirrors
_______ are images that are images that appear to be behind the mirror.

_______ mirrors are able to produce real images

_______ is the place where light beams meet after reflecting off a mirror

_______ is the type of mirror that is used to catch shiplifters in the act

An image will appear _______ if viewed in a concave mirror behind the focal point.
Unlike mirrors, lenses ______ light that passes through them.

Two basic lenses
are convex and
concave lenses
Concave Lenses
A lens that is thick on the ends and thin in the middle.

Image formed is always _______ and ________
Ray diagrams with lenses

Part 1. A ray is drawn from the top of the object through the middle of the lens.

Ray diagrams with lenses
Part 2. A line is drawn from the top of the object to
the lens parallel to the optical axis then refracted/reflected through the optical axis
Convex Lenses
These lenses are thicker in the middle and thin
on the sides.

Images that are produced can be ________ depending on ________.
Light and Vision
How does the eye work to create images?
Parts of the Eye




The Retina

Which part of the eye
is not working correctly?
A magnifying glass is used to create a virtual image that is magnified for you to observe.

Draw a ray digram showing how a magnifying glass works.
Lens and Cornea
The image produced by your eye is always
________ so objects you look at will always be ____________________.
What happens to the image as you bring it
closer to your eye?

Do you ever hit a point where no image is

Cornea-fixed lense that refracts light
Lens-an adjustable convex lens that
The lens is adjustable to ensure light is focused on
the ________
The rays need to converge on the retina of the eye.
Ray converge __________________
Rays converge __________
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