Science Grade 8
Unit 2: Optics
Chapter 4: Many properties of light can be
understood using a wave model of light
Name:_______________
Homeroom: __________
The history of light
Pythagoras
• A Greek philosopher
• Believed that beams of light were made of ___________________
• The ___________ detected these particles and could see the object.
Albert Michelson
• First person to measure the _________________________________ (3 x 108 m/s)
Speed: Light vs. Sound
Light: _____________ km/h
Sound: ____________ km/h
Thunder and Lightning
• Both the lightning strike and the roar of thunder happen _____________________________.
• You see the __________________ first.
• If you multiply the time in seconds between the strike and the roar by the ________________
________________, you will find the approximate distance.
Light technologies include:
1. _________________________
2. _________________________
3. _________________________
4. _________________________
5. _________________________
6. _________________________
7. _________________________
8. _________________________
9. _________________________
10. _________________________
Light
• A form of _______________ that can be detected by the __________________________.
Visible light
• A mixture of all the colors of a _______________________.
Properties of visible light
1. _____________________________________________________ Ex. Shadows
2. _____________________________________________________ Ex. Mirrors and Dust
3. _____________________________________________________ Ex. Bent stick effect
4. _____________________________________________________ Ex. Formation of a rainbow
5. _________________________________________________ Ex. light from sun reaching Earth
6. ________________________________________________Ex. Window pane vs. Frosted glass
Visible light spectrum: can be seen due to the _______________________ of light through a
_______________.
The constituent colors of white light are:
R ____________________
O ____________________
Y ____________________
G ____________________
B ____________________
I ____________________
V ____________________
wavelengths
*__________________ has the smallest refraction and __________________ has the greatest.
When a laser is shone through a prism, the light will refract but not disperse.
WHY? ____________________________________________________________________
__________________________________________________________________________
The Wave Model
Explains that light is a type of wave that travels through empty space and transfers energy from
one place to another.
*A peak is also called a _____________________.
Frequency
• The number of repetitive motions that occur during a given time.
Ex. The number of _____________________ that pass a point in 1 second.
• Measured in ________________.
Amplitude
• The height of a wave ___________________ or depth of a wave ______________________
as measured from rest position.
• Crest ____________________= Trough _______________________.
*The larger the amplitude, the greater the energy transported.
Wavelength
• The distance from crest to crest, trough to trough, or the distance covered by one complete
crest and one complete trough.
• Measured in _______________.
• Longer wavelengths refract the __________________.
Frequncy and wavelength
• High ______________________ waves have short ______________________.
• Low ______________________ waves have long ________________________.
Electromagnetic Radiation
• The transmission of energy in the form of _________________ that extend from the longest
radio waves to the shortest gamma rays.
Types of Electromagnetic Radiation
Types
Radio waves
Microwaves
What are they?
The longest _________________ and
lowest _______________ and
_________________.
Can be used to help us see the inside of
our bodies to diagnose illness.
Have the shortest ________________ and
highest ___________________ of all radio
waves.
Examples
Infrared waves
Longer _________________ and lower
_______________ and
_________________.
Infrared means below red.
Also called ______________ radiation
Visible light spectrum Can be continually detected by our eyes.
Ultraviolet waves
Shorter ___________________ and higher
___________________ and
__________________.
Very energetic.
Have the ability to kill bacteria in food,
water and medical supplies
X-Rays
Have a shorter __________________ and
higher _________________ and
______________________ than UV.
Gamma rays
Have the highest _________________ and
____________________ and the shortest
_____________________.
Positive and Negative Effects to Exposure to Electromagnetic Radiation
X-ray
Positive effects
Negative effects
Ultraviolet
Radio waves
Key Terms
Pythagoras_____________________________________________________________________
______________________________________________________________________________
Microscope____________________________________________________________________
______________________________________________________________________________
Telescope______________________________________________________________________
______________________________________________________________________________
Energy________________________________________________________________________
______________________________________________________________________________
Force_________________________________________________________________________
______________________________________________________________________________
Crest__________________________________________________________________________
______________________________________________________________________________
Trough________________________________________________________________________
______________________________________________________________________________
Wave_________________________________________________________________________
______________________________________________________________________________
Wavelength____________________________________________________________________
______________________________________________________________________________
Amplitude_____________________________________________________________________
_____________________________________________________________________________
Frequency_____________________________________________________________________
______________________________________________________________________________
Hertz_________________________________________________________________________
______________________________________________________________________________
Medium_______________________________________________________________________
______________________________________________________________________________
Transverse wave________________________________________________________________
______________________________________________________________________________
Compression wave______________________________________________________________
______________________________________________________________________________
Wave model of light_____________________________________________________________
______________________________________________________________________________
Visible light____________________________________________________________________
______________________________________________________________________________
Refraction_____________________________________________________________________
______________________________________________________________________________
Spectrum______________________________________________________________________
______________________________________________________________________________
Reflection______________________________________________________________________
______________________________________________________________________________
Radiant energy_________________________________________________________________
______________________________________________________________________________
Electromagnetic radiation_________________________________________________________
______________________________________________________________________________
Radio waves____________________________________________________________________
______________________________________________________________________________
Microwaves____________________________________________________________________
______________________________________________________________________________
Infrared waves__________________________________________________________________
______________________________________________________________________________
Ultraviolet waves________________________________________________________________
______________________________________________________________________________
X-rays_________________________________________________________________________
______________________________________________________________________________
Gamma rays____________________________________________________________________
______________________________________________________________________________
Goal • Use this page to review the Key Terms in Chapter 4.
1. List one common use for each type of radiation listed. Then use the types of radiation
to label the diagram below.
gamma rays
____________________________________________________________________
infrared waves
__________________________________________________________________
microwaves
____________________________________________________________________
radio waves
____________________________________________________________________
ultraviolet waves
________________________________________________________________
visible light
____________________________________________________________________
X rays
_________________________________________________________________________
____
Comprehension Questions
1. What made scientists think that light behaved like a wave, rather than a stream of particles?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
2.a) Who was the first person to accurately measure the speed of light?____________________
b) What is the speed of light? ________________________
3. How does the speed of light compare to the speed of sound?
______________________________________________________________________________
4. Explain why you can see lightning before you can hear thunder.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
5. How does a prism separate light into different colours?
______________________________________________________________________________
______________________________________________________________________________
6.
a) Which colour has the longest wavelength?
b) Which colour has the shortest wavelength?
c) Which colour has the highest frequency?
d) Which colour has the lowest frequency?
7. Which colour refracts more in a prism, yellow or blue?
_______________________
_______________________
_______________________
_______________________
_______________________
8. What is the difference between a crest and a trough?
______________________________________________________________________________
______________________________________________________________________________
9. How are the wavelength and frequency of a wave related?
______________________________________________________________________________
______________________________________________________________________________
10. Describe the difference between wavelength and wave amplitude.
______________________________________________________________________________
______________________________________________________________________________
11. Which type of electromagnetic radiation has the longest wavelength?
______________________________________________________________________________
12. What is another term for heat radiation? ___________________________________
13. What are three wavelengths on the electromagnetic radiation scale that are shorter than
visible light?
1. _____________________________
2. _____________________________
3. _____________________________
14. What are three wavelengths on the electromagnetic radiation scale that are longer than
visible light?
1. _____________________________
2. _____________________________
3. _____________________________
15. Name the kind of electromagnetic radiation likely to be used in each of the following
technologies:
a) TV broadcast signals: _____________________________
b) detecting a broken arm: _____________________________
c) examining the inside of a weld in a steel oil pipe _____________________________
d) lamp used to warm a baby chick _____________________________
e) measuring the speed of a passing car _____________________________
f) communicating between an aircraft and a control tower _____________________________
g) cellphone _____________________________