Script for
Light Magic
This slideshow is designed for lower primary. Main focus is to get students to look at teeth to help determine their position on the food web.
Slide 1.
·
Discuss with the students the subject of light.
What is light? Where does it
come from? Accept all answers even
if they are way out there! This is the time when you are finding out from them
what they know about science and their comfort zone with you!
Slide 2.
·
How
can we see light?
·
Use eyeball model, go over parts of the
eye, how light moves through. Our
eyes have adapted to sense light from the sun. Our eyes see the world upside
down and our brain turns the image right side up.
Slide 3.
·
Ask
the kids to come up with a hypothesis; why do aliens have big eyes?
·
If
aliens are from a planet far from sunlight, they would need big eyes to capture
light. Our face uses eyes to take
advantage of light.
Slide 4.
·
Light is
actually made of something called photons or electromagnetic radiation.
·
Prove it
to students by making light move.
·
Notice
that the “tree” flips when it goes through the lens.
·
The lens
is similar to our eye lens. Light is refracted.
Slide 5.
·
Compare
lenses and mirrors and their shapes.
·
If light
goes through it is refracted and scatters the light.
·
If light
encounters a mirror it will be reflected.
Slide 6.
·
Light is
part of the electromagnetic wave spectrum.
·
The
speed of light is 300,000 km/sec; can a rocket fly faster? Can a meteor fall
faster? (Speed limit of matter and energy).
·
Light can be reflected, refracted, or
diffracted. Light in motion can act like a wave and a particle.
Slide 7.
·
There
are 2 types of waves, physical and electromagnetic.
Sound is an example of physical; and light is a sample of
electromagnetic.
·
Use the
picture to see other examples from radio to x-rays.
·
Electromagnetic waves have the same speed.
Slide 8.
·
Wavelengths of visible light are measured in nanometers. Red light has a longer
wavelength than blue light, so blue has to wiggle extra to keep up with red.
·
When
light breaks up due to refraction you get the rainbow.
It is always in the same sequence, knows as ROY G. BIV.
Slide 9.
·
All
light travels at the same speed. Albert Michelson experimented with light to
determine its speed.
·
He refined earlier experiment conducted
by Leon Foucault.
·
Light
interacts with substances and objects. It is reflected, refracted, or
diffracted.
·
Refraction goes through a substance and because it is different type it will
deflect a little.
·
Reflection is when light bounces from the mirror surface.
·
Diffraction is when light goes through a small slit and shows a pattern and the
light branches out.
· Next activity is to see if you can determine what is refraction, reflection or diffraction.
Slide 11.
·
Reflection is when a wave bounces off a surface back toward the source. Have the
children hypothesize what happens to the image when it is reflected by flat,
concave, and convex mirrors stepwise respectively. Reinforce concave and convex.
Slide 12.
·
Refraction of light happens when waves are deflected as they pass through a
substance. (A change in direction of the wave due to a change in the medium it
passes through i.e. air, water, glass). Light travels through water and air at
different speeds. Different
wavelengths of light can be separated out from white light (dispersion)
using a prism.
Slide 13.
·
Diffraction occurs when a wave travels through a small opening and flares out
revealing a diffraction pattern.
Slide 14.
·
Light
can move as a wave and as a particle. A
light particle is called a photon.
·
Light
waves travel along a linear path but can change direction as they enter a
different medium (i.e. from air to glass/water). [F.Y.I. Wave propagates through
electric and magnetic fields].
Slide 15.
·
What
produces light? Many things-
Incandescence, excitation, fluorescence, and phosphorescence.
Slide 16.
INCANDESCENCE.
·
Light
emitted from an incandescent lamp is white . All the frequencies are
emitted. This had to do with the atom acting in a solid. Most
incandescent bulbs are made from tungsten, a solid.
·
Light is
emitted through radiation or heat. Stars give off light because of
radiation. The temperature of incandescent bodies depends on the color of
the radiation they emit.
Slide 17.
EXCITATION.
·
When an
electron is excited to a higher energy level, the atom is said to be excited.
The electron's higher level is only temporary, as it goes from high energy level
back to normal level.
·
The
atoms lose its temporarily acquired energy when the electron returns to a lower
level.
·
The
energy released is in the form of photons which our eyes see as light.
Light emitted from a neon sign is an example of excited neon gas.
Millions of electrons vibrate back and forth inside the glass tub and
smash into atoms, this constant bombardment and returning to the normal level
emits the characteristic red light of neon.
·
The
cycle of excitement to de-excitation.
Another example is the new type of mercury vapor street lights.
The light is emitted by the excitation of the vapors.
Not only is the light brighter, but it is less expensive and lasts longer
than incandescent lamps.
Slide 18. FLUORESCENCE.
·
When you
have some materials that are excited by ultraviolet light upon a de-excited
photon, you get fluorescence.
·
In a
fluorescent lamp, the tube is filled with very low pressure mercury vapor which
is excited by the impact of the high-speed electrons.
·
Upon
de-excitation, energy is released as a photon of light. Fluorescent paints can
cause it to glow red, yellow or some other color when bombarded with photons in
sunlight. If you put these same paints under ultraviolet lamps, the color
will be more intense.
Slide 19. PHOSPHORESCENCE.
·
Some
materials stay in an excited state longer than others.
·
As a
result there is time between the process of excitation and de-excitation.
This is called phosphorescence.
·
Atoms
are excited by visible light. The afterglows may last from fractions of a
second to hours, even days to years.
Slide 20.
·
Products
from light “Photonics” is the exploration of light in devices and systems.
Slide 21.
·
TVs and
Computer screens use pulsating pixels of red, blue, and green in patterns that
allow our eye to see them as an image of many colors.
·
Red,
blue, and green light is added together in various ways to reproduce a large
variety of colors.
·
High
definition TV, has an added yellow.
Slide 22.
(L.ight
A.mplification
S.imulated E.mission of
R.adiation)
·
Laser is
coherent light, meaning all the wavelengths march together. [F.Y.I. Basis can be
found in (Einstein coefficients) for the absorption, spontaneous emission, and
stimulated emission of electromagnetic radiation.
·
In the
laser beam all new photons enter the electromagnetic field with identical phase,
frequency, polarization, and direction]
Students must
first understand two terms: coherent
and incoherent light. Light emitted
by normal means such as a flashlight or a bulb, is incoherent; meaning that the
photons of the many wave frequencies of light are oscillating in different
directions. It is not a stream of
light. Coherent light is a beam of
photons (almost like particles of light waves) that have the same frequency and
are all at the same frequency. Only
a beam of laser light will not spread and diffuse.
In lasers, waves are identical and in phase, which produces a beam of
coherent light. There are many types
of lasers that use gases such as helium, neon, argon, and carbon dioxide.
Lasers also use semiconductors (Galiodium and Arsenic), solid-state
material (ruby, glass), and even chemicals (hydrofluoric acid) in their
operation.
Slide 23.
·
Cameras
use incoherent light to make 2D images (film or digital).
·
3D
images are made with coherent light (lasers). This is a hologram.
Slide 24.
·
Light
can carry information. Fiber Optics uses special fibers and total internal
reflection to keep light traveling along a directed path.
Slide 25.
Photonics
·
There
are still many products that can be developed with the understanding of light