Science Grade 8Unit 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 ModelExplains 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 What are they? ExamplesRadio waves The longest _________________ and

lowest _______________ and _________________.Can be used to help us see the inside of our bodies to diagnose illness.

Microwaves Have the shortest ________________ and highest ___________________ of all radio waves.

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 Ultraviolet Radio wavesPositive effects

Negative effects

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 _____________________________