Unit 7 - Optics

What is the electromagnetic spectrum?

How does AM and FM show how wavelength correlates with travel distance?

It is a spectrum of electromagnetic radiation with the left having the shortest wavelengths and shorter travel distance under IDEAL CONDITIONS

-AM wavelengths are longer than the FM ones so it theory they should travel longer but they DON'T

--> This is due to AM waves having less energy so stuff interfere with it more IRL (trees, buildings).

--> FM waves (more energy) get less interference

What do these symbols mean?

di, do, hi, ho

--> What are the relationships between an object and a plane mirror (flat mirror)?

di = image distance

do = object distance

hi = image size

ho = object sive

--> In a plane mirror, di=do and hi=ho due to the law of reflection

What are the 4 steps to drawing the image coming from a object to a plane/flat mirror?

1. Draw a horizontal line from the top of the object to mirror and label it d_o

2. Extend the line an equal distance behind mirror on virtual side and label it d_i

3. draw the object from equal dist marked in prev step with equal height to the image and label h_i

4. Draw any angles based on Q (Law of reflection will apply)

What are the 3 characteristics of an image in a plane/flat mirror?

1. Image is the same size as the object

2. Image is vertically erect/upright

3. The image is virtual

What is Light?

What are 2 facts about Light?

- Light is a form of radiant energy that the eye can detect.

1. We see objects because light is reflected or emitted from them.

2. ⚠Light is a transverse wave AND a particle (Einstein)(Wave Model)⚠

What is the difference between Luminous and Non-Luminous Objects?

What is the difference between Reflection and Refraction?

Luminous object = produces light, so are seen by their own light (candle, flames, sun, lightbulb)

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Non-Luminous object = does not emit their own light but they REFLECT light from another object (Moon, Earth)

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Reflection = light rebounding from a shiny surface (laser light in mirror and light can be seen in fog)

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Refraction = light bends as it travels from one medium to another (straw in water or sunlight on hot pavement)

What is the Particle Model?

What is the Wave Model?

What is the Quantum Model (particle and wave theory)?

--> How does light travel in a Vacuum, in air, and how can we show its path?

Particle Model = Light is particles radiating from the source

Wave Model = Light is transverse waves radiating away from the source

Quantum Model = Light are photons with wave properties

--> Light travels in a straight line in a vacuum, uniform in a medium like air (cus we assume Vacuum and Air have the same index of reflection(N) )

• we can show the path of light as a model in RAY OPTICS

Define:

- Translucent

- Transparent

- Opaque

- Parallax

- Translucent = transmits light (lets light in but not image) (EX: frosted glass)

- Transparent = glass (see through) (EX: window)

- Opaque = does not let light pass (EX: wood)

- Parallax = Apparent motion of an object nearby with reference to a more distant object.

(put finger in front of you and then switch eyes)

What is the value we will use for the speed of light in this Unit?

What are the 2 formulas?

Speed of light = 3 x 10^8 m/s

formula: C=fλ OR C = nv

What is the index of refraction?

The index of refraction = the ratio of speed of light in a vacuum to speed of light in a given material.

—> use the formula to get speed of light (C = fλ) and compare to 3 x 10^8 m/s)

What is the formula for the Index of Refraction?

n = c/v where,

n = index of refraction

c = 3x10^8 m/s (constant)

v = actual speed of light (C= Fλ)

When looking at the normal line in refraction, what must we remember about light going from a less dense to a more dense medium?

If Light goes from a less dense to a more dense medium, it bends TOWARDS the normal line.

What are the 4 Characteristics you MUST say after drawing a Ray Diagram?

(SALT)

Size = image is same size/larger/smaller

Attitude = image is Inverted/Upright

Location = between C and F or etc...

Type = image is real/virtual

What are the general pattern light rays follow for CONCAVE and CONVEX mirrors

—> what does it mean you have to do for Convex mirror ray diagrams?

Concave mirrors will keep light rays on the real side

Convex mirrors will put light on virtual side (this means you will use DOTTED LINES‼️)

What is:

- The Principal Axis (PA)?

- Centre of Curvature (C)?

- Focal Point/ Focus (F)?

- Vertex?

Principal Axis = Horizontal line drawn right in the middle of the curved mirror

Centre of Curvature = If a Convex/Concave mirror was drawn out as a full circle, C would be the centre point of it and Vertex marks the radius

Focus = focal length of the mirror (length from centre marked as vertex to the farthest curved point of the mirror which are the top and bottom)

Vertex = one the Principal Axis line and marks the true centre of the mirror in both X and Y axes

What are the 3 Steps you MUST follow when drawing the light rays for a Concave/ Convex mirror

1. Draw a parallel line to the PA from the top of the object to the top of the mirror and then down through the focus

2. Line from top of object through the focus, hit the bottom of the mirror, then parallel to the PA

3. Top of object through C to the bottom of the mirror

• What’s a cool way to remember if the image will be bigger/smaller/same?

What are the 5 cases for Concave Mirrors and what is the SALT of the image?

• Think of C as the centre point.

  • If object is behind, image will be SMALLER

  • if object is in front, image will be BIGGER

  • If object is on C then SAME size

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1. Object to the left of C = smaller, inverted, between F and C, and real

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2. Object on C = same size, inverted, closer to C but between F and C, real

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3. Object between C and F = bigger, inverted, behind C, real

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4. Object on F = NO IMAGE

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5. Object to right of F (will be on virtual side)—> you will need to do step 2 differently (through F, touch top of object, touch top of mirror and perpendicular to left BUT extend to virtual)

= Bigger, upright, past the mirror and to the right of Vertex, VIRTUAL

What are the 3 special cases in Concave mirror Ray Diagrams?

1. When object is directly on F, NO image can be made

2. When object is to the right of F, for step 2, draw a line going through F, the top of object, and then the top of mirror, then go left perpendicular, and extend ALL LINES to the virtual side

3. Image will be INVERTED if object is DIRECTLY on C or to the left of C or between C and F (this image will also be behind object and is the hardest to get all 3 lines to come to a point)

Test Q: Why would you use a Concave mirror for camping?

you use a Concave mirror for camping cus it actually focuses light to one point which may allow you to start a fire????

What are the 2 cases for Convex Mirrors and what is the SALT of the image?

1. Object is upright —> smaller, upright, between V and F, virtual AND (for step 2, do a parallel line AND one that goes through focus)

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2. Object is inverted —> smaller, inverted (shows that image follows orientation of OG object), between V and F, virtual (same thing for step 2, draw parallel AND one going through focus)

What is the Thin Lens Equation?

What is the Magnification of Lenses Equation?

(What MUST you remember about the units of these and for this UNIT?)

The units will ALWAYS be in CM for this Eq and also for everything else in this UNIT

What are the 5 Sign conventions you should memorize?

1. Focal length sign is the opposite of what you’d normally expect (cus real side is + and on left and virtual is - and on right side)

2. d_o will always be positive as it is on the real side

3. d_i changes with which side image is on

4. h_i and h_o follow wether image is upright (+) or inverted (-)

5. Magnification follows wether image is upright (+) or inverted (-)

What must you remember to do before the test?

RE READ ALL OF THE NOTES

--> Note the index of refraction values

--> Look at drawn diagrams

What does Mrs. Smith want us to know about Roemer and Huygens?

1. Roemer and Huygens calculated that light took 22 minutes to cross Earth’s orbit (diameter which they considered as 3 × 10¹¹ m)

2. The actual time (what we use today) is 16 minutes or 960 seconds

What may Smith want us to know:

• What was Roemer famous for?

• What was Huygens famous for?

• Roemer was famous for being the FIRST person to estimate/create the speed of light value.

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• Huygens was famous for being the one who created the wave theory of light (“Light is transverse waves radiating away from the source“)

What are Concave Mirrors Called?
What are Convex Mirrors Called?

Concave = Converging

Convex = Diverging

What are the 6 N values you should know?

1. Vacuum = Air = 1

2. Water = 1.33

3. Ethanol = 1.36

4. Quartz = 1.46

5. Crown glass = 1.52

6. Diamond = 2.42 (Nothing will be greater than diamond’s index of refraction)