The nature of light and the electromagnetic spectrum
1.
What is the relationship between the wavelength of light, and the amount of energy it carries?
Shorter wavelength = More energy (think of waves crashing on a dock)
2.
List the types of EM radiation in order, from low energy to high energy: visible light, ultraviolet, gamma rays, radio waves, X-rays, infrared, microwaves
Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
The production of light
3.
Define luminous.
An object that produces its own light.
4.
Explain how light is produced by each of the following methods: a.
incandescence – light is produced by a glowing hot object b.
fluorescence – UV light is absorbed by an object, and released as visible light immediately in a fluorescent light, electric current excites molecules of Mercury, which emit UV. The phosphor coating in the bulb absorbs it and emits as visible light. c.
Phosphorescence - UV light is absorbed by an object, and released as visible light slowly (glow in the dark objects) d.
Chemiluminescence – chemical reactions produce light, with little or no heat e.
Bioluminescence – chemiluminescence in a living organism f.
electric discharge – current is passed through gas molecules, causing them to become excited and glow
5.
Why is incandescence considered an inefficient form of light production?
Most of the energy that goes into powering an incandescent light bulb is converted to heat. (Light is the byproduct of heat production)
6.
Compare and contrast fluorescence and phosphorescence.
Similar – UV light is absorbed and visible light is released
Different – fluorescence is immediate; take away the UV source and light production stops.
Phosphorescence is gradual; the object continues to glow even after the UV source is removed.
7.
Compare and contrast chemiluminescence and bioluminescence.
Similar – chemical reaction produces light
Different – bioluminescence is just more specific; it occurs in living organisms
The ray model of light
8.
State Fermat’s principle.
Light takes the path that is fastest.
9.
What type of path does a ray of light follow?
Straight line
10.
What factor influences the size of an object’s shadow? Explain.
Distance of object from light source. Closer object blocks more light rays  shadow is bigger
11.
What factor influences the sharpness of an object’s shadow? Explain.

Size of light source. When the light source is large, more light rays are emitted and from all parts. Smaller light sources produce sharper images.
12.
What are the umbra and penumbra of a shadow?
Umbra – dark part of shadow; all rays are blocked
Penumbra – “fuzzy” parts of shadow; only some rays are blocked
13.
What are the three ways in which light can behave when it contacts an object?
Transmit, reflect, absorb
14.
Identify the behaviour of light when it contacts an object that is: a.
Transparent – all transmitted b.
Translucent – some transmitted, some absorbed c.
Opaque – all absorbed or reflected (none transmitted)
Reflection
15.
A light ray strikes a reflective surface at an angle of 25° from the normal. What will be the angle of reflection?
25°
16.
Draw a diagram that illustrates the law of reflection. Label the following: reflective surface, incident ray, reflected ray, normal, angle of incidence, angle of reflection.
17.
List the characteristics (LOST) of an image formed in a plane mirror.
L – behind mirror, as far as object is in front
O – upright
S – same as object
T - virtual
18.
What is the difference between a real image and a virtual image?
Real image – reflected light rays meet in front of the mirror
Virtual – reflected rays never meet; they only appear to meet behind mirror
Curved mirrors
19.
Why are concave mirrors also called converging mirrors, and convex mirrors called diverging mirrors?
Light rays that reflect off of a concave mirror will converge. Those that reflect off convex mirrors will diverge.
20.
Draw ray diagrams and locate the images of object in concave mirrors when: a.
The object is beyond the focal point c. The object is at the focal point b.
The object is within the focal point
SEE YOUR TEXTBOOK FOR THESE DIAGRAMS
21.
Draw a ray diagram in order to locate the image of an object formed in a convex mirror.

Mirror
Plane
SEE YOUR TEXTBOOK FOR THESE DIAGRAMS
22.
Identify the relationship that exists between the orientation of an image, and its type.
Real images are always inverted; virtual are upright
23.
Complete the table below, which lists the characteristics of images formed in mirrors:
Distance of object from mirror
Any distance
Location
Behind mirror, as far as object
Orientation upright same
Size Type
Virtual
Concave Beyond F Can be closer or farther, depending on location of object
Inverted Can be either smaller or larger real
At F NO IMAGE
Between F and mirror
Any distance
Behind mirror Upright
Behind mirror Upright
Larger
Smaller
Virtual virtual Convex
24.
Identify which type of mirror (plane, concave, or convex) is used for the following applications, and explain why: a.
shaving mirror (magnifies object) – concave; larger upright image b.
security mirror – convex; increases field of view c.
flashlight – concave; reflects rays from bulb in a parallel beam d.
full-length mirror in clothing store – plane; upright image, same size e.
car headlight - concave; reflects rays from bulb in a parallel beam f.
make-up mirror (magnifies object) – concave; larger upright image g.
solar oven – concave; reflects light rays to focal point to cook food h.
bathroom mirror – plane; upright image same size
25.
The mirror equation and the magnification equation can be used to predict the characteristics of images formed in curved mirrors. a.
On the two diagrams of curved mirrors below, label the following: f, d i
, d o
, h i
, h o b.
Which of the above is concave? Convex?
First is concave; second is convex c.
When is the value of f negative?
When the focal point is behind the mirror (convex mirror) d.
When is the value of d i
negative?
When the image is located behind the mirror (virtual image therefore upright) e.
When is the value of h i
negative?

When the image is inverted (therefore real)
26.
a. A 3-cm tall object is placed 25 cm in front of a concave mirror that has a focal length of 10 cm.
Determine the distance of the image from the mirror. b. Determine the height of the image. c. Use LOST to list the image characteristics.
[Ans: +16.7 cm]
[Ans: - 2.00 cm]
[L – In front, closer; O – inverted; S – smaller; T - real]
27.
a. A 6-cm tall object is placed in 7 cm front of a convex mirror that has a focal length of 28 cm. Determine
the distance of the image from the mirror. [Ans: -5.6 cm] b. Determine the height of the image. c. Use LOST to list the characteristics of the image.
[Ans: +4.8 cm]
[L – behind; O – upright; S – smaller; T - virtual]
Refraction and total internal reflection
28.
What is refraction, and why does it occur?
Bending of light that occurs when light passes from one medium to another; occurs because light changes speed.
29.
When light enters a new medium, in which direction will it bend when it: a.
slows down – towards the normal b.
speeds up – away from normal
30.
In which substance will light travel slower? Substance A (n=1.65) or Substance B (n=1.57)?
31.
Substance A – it has the larger index of refraction.
Light travels at a speed of 2.05 x 10 8 m/s in fused quartz. Calculate its refractive index. The speed of light in a vacuum is 3.00 x 10 8 m/s. [Ans: 1.46]
[Ans: 1.69 x 10 8 m/s] 32.
The refractive index of sapphire is 1.77. How fast does light travel in sapphire?
33.
What is the critical angle of a medium?
The angle of incidence that produces a refracted angle of 90 degrees.
34.
State the two requirements for total internal reflection to occur.
(1) n2 is less than n1, so that light bends away from the normal
(2) the incident angle exceeds the critical angle
35.
Can total internal reflection occur if light is traveling from water (n=1.33) into flint glass (n=1.57)? Explain.
No. in this case, n2 is larger than n1.
36.
Describe an application of total internal reflection.
Retroreflectors – Tiny triangular prisms reflect light back in the direction that it came from.
Fibre optics – Light rays are reflected internally within a cable; can be used for telecommunications.
Optical phenomena
37.
What is dispersion?
The separation of white light into its component colours. It occurs because each colour of light has a slightly different speed, so when they are refracted they refract at slightly different angles.
38.
How does a rainbow form?
Dispersion of light in water droplets in the atmosphere.
39.
How is the formation of a rainbow similar to the formation of sundogs? Different?
Similar – Light is dispersed in the atmosphere.
Different – Rainbows – dispersion is in water droplets; sundogs – dispersion is in ice crystals.
40.
When viewing an underwater object from above the water, how does the apparent location of the object differ from its actual location? Draw a ray diagram to support your answer.
The object appears closer to the surface than it actually is.

41.
How are shimmering and mirages formed?
Hot air is less dense than cold air. Light bends as it passes through air that has different temperatures.
42.
What is the difference between an inferior and a superior mirage?
Inferior – image forms below the object; occurs when air near surface is hot
Superior – image forms above object; occurs when air near surface is cold