Miss Nevoral
Science 8
Optics Unit
http://www.sd23.bc.ca/~lnevoral
Chapter 10 – Sources and Properties of Light
KEY
Name: _____________________
Date: ____________
Block: ________
Section 10.1 – Light Energy and Its Sources (pages 289 – 293)
1. Define light: A form of energy that can be detected by the human eye.
2. Copy and paste Figure 1 on page 289 in the space below. Explain how we can see
light.
3. Define luminous: an object that emits (gives off) its own light.
4. Define nonluminous: reflects light from other sources.
5. Which of the following are luminous?
a) a campfire - luminous
b) the Moon - nonluminous
c) a hot toaster filament - luminous
6. What are common forms of input energy that can be transformed into light energy?
Chemical, electrical, nuclear, and thermal E
7. Define incandescence: the process of emitting light because of a high
temperature.
8. Explain how an incandescent light bulb works. Electricity passes through a
tungsten filament (fine metal) which makes the wire very hot when the
bulb is turned on. Electricity light and heat energy
9. Explain, in your own words, the difference between a phosphorescent light
source and a fluorescent light source. Phosphorescent light is when
phosphors emit light after receiving energy from another source.
Fluorescence does a similar thing, but electricity is passed through a tube
which causes mercury vapour to emit UV energy. This UV energy is
absorbed by phosphors coating the inside of the tube and this is the light
energy you can see. Once the electricity is turned off, then the phosphors
stop working. Fluorescent lighting uses phosphorescence and electric
discharge.
10. Give two examples of light from electric discharge. Lightning, neon signs
11. Describe how the process of chemiluminescence. How is bioluminescence
similar to this? The process of changing chemical energy into light energy
with little or no change. Bioluninescence does the same process within
living things (fish, squid, bacteria, fungi, fireflies)
Section 10.2 – How Light Energy Travels (pages 294 – 297)
1. Define rays: The straight path/line of light produced by a light emitting
object.
2. Define shadow: The dark area which no light rays can reach; usually
behind an opaque object.
3. Do light rays travel in straight lines or curves? What evidence is there to support
this fact? How is a light ray represented? Light rays travel in straight lines.
The existence of shadows behind objects support this. Rays are
represented with a arrow 
4. Explain how solid objects cast a shadow. Light rays cannot pass through an
object; therefore, they can not reach the area behind; therefore, shadows
are formed.
5. What is an umbra? How does a penumbra form? The darkest part of a
shadow (no light from the source can reach here). The lighter part of a
shadow, some light from the source reaches here.
6. Why can you not see an object when it is behind another object? Light rays
cannot reach the eyes if they travel in a straight line from the source if
the source is behind another object.
7. Think about walking down a street lit by streetlights at night. What happens to
your shadow as you get farther away from the light? As you walk farther away
from a light source the shadow gets longer.
8. Suppose you are standing by the side of the road. You know that there are several
telephone poles farther along the road, but you can only see the one closest to you.
IF all the telephone poles are the same distance from the edge of the road, is the
road straight or curved. Explain your answer. The road is straight because if
you can only see 1 pole, then all the others are directly behind in a line
(since you can’t see them, they must be directly behind). If all poles are
the same distance from the road, then the road is straight.
9. On a sunny day, when do you think your shadow will be the shortest? The
shadow will be the shortest when the sun is directly overhead (therefore,
@ ~ noon).
10. Name two ways that life would be different if light DID NOT travel in straight lines.
You would be able to see around corners, no night time, no cold nights,
etc.
Section 10.3 – Getting in Light’s Way (pages 296 – 298)
1. Describe how light is affected by:
a) a transparent object – transmitted
b) an opaque object – absorbed/reflected
c) a translucent object – transmitted/reflected
2. Complete the table below. In the second column, classify each material as
transparent, opaque, or translucent. In the third column, state whether light is
absorbed, reflected, or transmitted when it strikes the material.
Material
Milk
Apple juice
Wax paper
Aluminum foil
Plastic wrap
Mirror
Helium
Ice cube
Smoky air
White paper
Newspaper
Cardboard
Clear plexiglass (hockey rinks)
Coloured plexiglass (alternate)
Rubber
Copper plate
Classification
Translucent
Transparent
Translucent
Opaque
Transparent
Opaque
Transparent
Transparent (w/o air
bubbles)
Translucent
Translucent
Translucent
Opaque
Transparent
Transparent
Opaque
Opaque
Behaviour of Light
Transmitted/reflected
Transmitted
Transmitted/reflected
Absorbed/reflected
Transmitted
Absorbed/reflected
Transmitted
Transmitted
Transmitted/reflected
Transmitted/reflected
Transmitted/reflected
Absorbed/reflected
Transmitted
Transmitted
Absorbed/reflected
Absorbed/reflected
3. Explain how climate is an important factor in deciding what type of building
materials to use when constructing a house. Hot climate  reflect sunlight;
therefore, light colours or shiny materials (metal roof). Cold climate 
darker material for siding and roof, dark colours, stucco or rough surfaces
4. Why does fall and winter clothing usually come in darker colours, while spring and
summer clothing usually comes in lighter colours? Dark colours absorb energy
from the Sun and light colours reflects light (keeps people cooler).
Section 10.4 – The Visible Spectrum (pages 299 – 300)
1. Define visible spectrum: The band of colours you can see. A set of colours
in white light (ROYGBIV)
2. What are the spectral colours and in what order do they occur? What
abbreviation can you use for these colours? The spectral colours are a set of
colours in white line. Red, orange, yellow, green, blue, indigo, violet
(ROYGBIV)
3. Who discovered that colour is a property of visible light? What did he use to test
his theory? How did he show that when colours are combined, they form white
light? Isaac Newton. Newton used a prism to split white light into
colours. He then used a second prism to combine the colours back into
white light.
4. Define prism: A clear object which can separate white light into all it’s
colours.
5. How does a prism separate light into different colours? Light travels at different
speeds inside the prism. This causes each colour to change direction
(refract) in a slightly different amount. Red the fastest and violet the
slowest.
6. How is a rainbow created? Why does this happen? The white light from the
sun is split into the separate colours of the spectrum because the
raindrops are acting like prisms.
7. What is “white light”? What colours make up white light? White light is the
light seen when colours of the spectrum are combined. ROYGBIV colours
make up white light.
8. Why does a sweater appear to be red? Include terms “reflect” and “absorb” in your
answer. White light hits the sweater and all colours except red are
absorbed (red is reflected and hits your eye).
9. A black shirt appears black because all the colours are? Absorbed
10. What colours of light are reflected by a white piece of paper? What colours are
reflected by a black piece of paper? All colours are reflected by a white piece
of paper. No colours are reflected by a black piece of paper (absorbed).
Section 10.5 – The Electromagnetic Spectrum (pages 301 – 305)
1. Light energy is a form of what kind of energy? Radiant energy
2. The electromagnetic spectrum represents the different forms of electromagnetic
radiation.
3. What is one important property of all electromagnetic radiation? It can
travel through a vacuum (no substance is needed to transmit it).
4. What is the speed of light? 300 000 km/s
5. Electromagnetic radiation is made up of waves having different wavelengths and
frequencies.
6. Looking at the diagram below, label and describe parts 1-5.
1) Crest – highest point of wave
2) Trough – Lowest point of wave
3) Amplitude – height of crest from resting position
4) Wavelength – crest to crest or trough to trough
5) Rest position – ground zero. Crest and trough are determined from
this position
7. Define frequency and its unit: The number of occurrences in a period of
time; in waves, the frequency is the number of wavelengths in a period of
time.
8. Use the diagram found below to answer the following questions.
a) How long is the wavelength of the wave below?
4 meters (5m – 1m)
b) How large is the amplitude of the wave below?
2 meters
9. Use the diagram found below to answer the following questions.
a) Which wave below has the smaller amplitude, A or B?
b) Which wave carries more energy, A or B?
B
A
10. Use the diagram found below to answer the following questions.
a) What is the same for waves X and Y: amplitude, wavelength, or frequency?
amplitude
b) Which wave has a greater frequency, X or Y?
Y
c) Which wave has a longer wavelength, X or Y?
X
11. Assuming that the speed of a wave is constant, explain the relationship between
wavelength and frequency. As the wavelength increases, the frequency
decreases. As the wavelength decreases, the frequency increases.
12. Place these electromagnetic waves in order from lowest energy to highest
energy: blue light, microwaves, X-rays, orange light, infrared radiation.
Microwaves, infrared, orange, blue, X-rays
13. Place these electromagnetic waves in order from shortest wavelength to
longest wavelength: visible light, gamma rays, radio waves, ultraviolet light.
Gamma rays, ultraviolet, visible light, radio waves
14. List the electromagnetic waves you have experienced in the past year and where
they are found in the electromagnetic spectrum. UV rays, microwaves, radio
waves, visible spectrum