Optics Test

Study this PowerPoint

What is an optical Illusion?

• A perceived image that is different from reality. The eye gathers information that the brain tries to understand.

How can we view light energy?

• Sun

• Colour

• Mirrors

Facts about light• Light didn’t appear until nearly half a million years after the Big Bang• Light moves at 186, 000 miles per second• Light has a hard time moving through a diamond, this is what causes the

sparkle• Eyeglasses bend light as it travels from the air to lens, fixing vision problems• Ancient Greeks thought we could see by shooting light from our eyes• People are bioluminescent and are brightest around noon, around the lips

and cheeks• 90% of all sea creatures below 1500 ft give off light• 100 W light bulb can produce 325 F in a confined space• Visible light makes up one ten-billionth of the electromagnetic spectrum • Some animals like bees, birds and lizards can see ultraviolet light

Questions: 268-277

1. What is the most important source of natural light?

2. What are the 6 sources of light what does each mean?

3. What happens when light strikes an opaque surface?

4. What the 3 properties used to describe the amount of light energy absorbed or reflected?

5. What are the 4 characteristics of an image?

Answers:

1. Sun is the most important source of natural light.

3. When light hits an opaque surface no light can transmit through and all light is either absorbed or reflected.

4. Colour, sheen [shininess] and texture are the 3 properties that describe the amount of light energy reflected or absorbed.

5. Four characteristics of an image; size, attitude, location, and type.

Answers

2. Six sources of light: Incandescence-light produced by high temperature Phosphorescence-light produced through absorbing

energy from another source Electric Discharge-light produced by electricity passing

through a gas [neon] Fluorescence-light produced by using electric

discharge and phosphorescence Chemiluminescence-light produced by changing

chemical energy into light energy Bioluminescence-light produced by living things

through a chemical process in their bodies

What is rectilinear propagation?

• The idea that light travels in straight lines from a source.

What is the particle-wave duality?

• The idea that light moves in both straight lines and in waves.

Degrees of Transparency

Material Degree of Light Examples

Transparent Particles let light through easily; images are easy to see

Plastic wrap, glass, air, shallow water

Translucent Particles let light in, but reflect light as well, making images not clear to see

Frosted glass, clouds, skin, fingernails

Opaque Particles do not allow any light through; light is absorbed or reflected

Wood, stone, brick or most building materials

Compact Fluorescent Bulb vs. Incandescent Bulb

• Contains a gas which produces UV light when electricity is added

• Does not use heat to create light

• More energy efficient than Incandescent bulbs

• 30% of energy emitted is heat

• Creates light by heating a filament in the bulb

• The energy used to create the heat is wasted

• Has a shorter life span than CFB

• 90% of the energy emitted is heat

Reflection

• Reflection occurs when light is returned after hitting a surface. Most surfaces reflect some light, otherwise we wouldn’t see them or their colour.

• Rough surfaces reflect light in many directions, so we see very little light.

Reflecting Light

• The Normal—the line drawn from the point of incidence at 900 to the surface of the optical device

• Incident Ray—a ray of light that travels toward a reflecting surface

• Angle of Incidence—is the angle between the incident ray and the normal

• Angle of Reflection—the angle between the reflected ray and the normal

• The point of incidence—the spot where the incident ray strikes the reflecting surface

Reflection

90 Degree Angle

Reflecting Surface [Mirror]

Incident Ray

Angle of Incidence Angle of

Reflection

Normal

Reflected Ray

Laws of Reflection

• The angle of incidence is equal to the angle of reflection

• The incident ray, normal, and reflected ray all lie on the same plane

Plane Mirrors

• Plane mirrors always produce virtual images

• The images of plane mirrors are always upright and located behind the mirror

• Plane mirrors show the image of the object, not the object itself

Characteristics of Concave Mirrors

• Concave mirrors “cave” inward• Concave mirrors can produce both real and

virtual images• Concave mirrors focus parallel light rays• Concave mirrors can be used in devices to send

light in a bean [flashlights]• Concave mirrors are used in reflecting

telescopes to gather light from objects in space• Concave mirrors can produce a large image of a

nearby object

Examples of Concave Mirrors

• Cosmetic Mirrors

• Solar Cookers

• Reflecting Telescopes

• Car headlights

Characteristics of Convex Mirror

• Convex mirrors bulge outward• Convex mirrors always produce virtual

images• Convex mirrors can be used to monitor

large areas; it has a wider view than any other mirror

• Convex mirrors always produce images that upright and smaller than the object

Examples of Convex Mirrors

• Surveillance mirrors

• School bus side mirrors

• Cosmetic mirror for enlarging images

Light Facts

• Light travels in a straight line

• Light travels at 300,000 km/s

• When light hits a transparent surface, most of the light enters the material

• Light refracting when it hits hot air creates mirages

Refraction: How does it work?

• Light refracts when it travels from one material to another. Light refracts when it travels through air then hits a lens, or when it travels through air and hits water.

Refraction: How do materials effect refraction?

• The speed of light differs from one material to another. The thicker the material, the slower the light travels. The change in speed causes the light to change direction.

• Air=1.00• Water=1.33• Diamond=2.42

Refraction

NORMAL

Incident Ray

Refracted Ray

Angle of Incidence

Angle of Refraction

Angle of Incidence is always greater than the Angle of Refraction

Material of Refraction

What is Optics?

• Optics is the science that studies the origin and spreading of light, how it changes, what effects it produces, and other phenomena associated with it.

What are the two branches of Optics?

1. Physical Optics—this branch is about the nature and properties of light

2. Geometrical optics—this branch is about the how images are formed with mirrors, lenses, and other optical devices

Optics Test Review

• Write your answers on a long sheet of paper.

1: List 3 examples of Convex Mirrors 3pts

• Surveillance mirrors

• School bus side mirrors

• Cosmetic mirror for enlarging images

2: What is one of the 2 laws of reflection? 4 pts

• The angle of incidence is equal to the angle of reflection

• The incident ray, normal, and reflected ray all lie on the same plane

3: What are 3 ways to view light energy? 3 pts

• Sun

• Colour

• Mirrors

4: What are the density values for Air, Water and Diamonds? 3pts

• Air=1.00

• Water=1.33

• Diamond=2.42

5: The line drawn from the point of incidence at 900 to the surface of the optical device

is: 1pt

• The Normal

6: What are the 6 sources of light? 6pts

IncandescencePhosphorescenceElectric DischargeFluorescenceChemiluminescenceBioluminescence

7: The angle between the reflected ray and the normal

is: 1 pt• Angle of Reflection

8: What is the most important source of natural light?

1 pt• The Sun

9: What are the 4 characteristics of an image? 4pts

• Four characteristics of an image; size, attitude, location, and type.

10: What are the 2 types of light bulbs? 2 pts

• Incandescence and Compact Florescence

11: How fast does light travel? 1pt

• 186,000 m/s or 300,000 km/s

12: The spot where the incident ray strikes the reflecting surface

is: 1pt• The point of incidence

13: What are the 3 types of mirrors? 3pts

• Plane

• Concave

• Convex

14: Angles of incidence and reflection are always: 1pt

• Equal

15: Angle of Incidence is always _______ than the angle of

Refraction: 1 pt• Greater than

16: Write the formula to calculate the number of images seen in

mirrors on angles: 1 ptNumber of images=(3600/angle between

mirrors)-1

17: What type of mirror can produce both real and virtual

images? 1 pt• Concave mirror

18: This type of bulb produces 30% of its energy as heat. 1pt

• Compact Florescent

19: List 3 examples of Concave mirrors: 3pts

• Cosmetic Mirrors

• Solar Cookers

• Reflecting Telescopes

• Car headlights

20: Convex mirrors always produce_________ images: 1pt

• Virtual