Ch 10 Physics

Question 1

What is light and how does it travel?

Answer 1

→ Some properties of light are easy to observe. For example, light travels at high speeds (nothing can move faster than light!).
→ Scientists call a small packet of light energy a photon.
→ Light travels in straight lines. When you turn on a flashlight in a dark room with dust in the air, you can see a beam of light in a straight line

Question 2

What is a medium and what requires a medium?

Answer 2

→ Most energy, like sound, heat, electrical energy all require a medium to be transmitted.
→ For example, heat energy can be transferred by conduction (touching) or convection (mixing). Both methods involve particles to transfer heat.
→ A medium is any physical substance that acts as a carrier for the transmission of energy

Question 3

How is light unique?

Answer 3

→ Light, however, is unique. It can travel through the vacuum of outer space (electromagnetic radiation, including visible light, can propagate through empty space without any medium to carry its energy). Light does not require a medium to be transferred because it is self propagating.
→ Light is transferred through radiation. Radiation does not require a medium to transfer energy and the energy still travels at the speed of light.
→ Under certain conditions, light shows wave like properties
→ All waves have a wavelength and amplitude

Question 4

What are the different types of electromagnetic waves and how are they classified?

Answer 4

→ Some examples are: microwaves, X-rays and visible light which the human eye can detect.
→ Electromagnetic waves are classified based on the energy of their wave
→ We call objects that produce their own light, luminous
→ Objects that do not produce their own light are non-luminous
→ Short wavelengths are dangerous

Question 5

What is Incandescence?

Answer 5

Description: The production of light as a result of high temperature

Examples: Molten metal, incandescent bulbs, fire

Question 6

What is electric discharge?

Answer 6

Description: The process of producing light by passing an electric current through a gas

Examples: Lightning, Neon signs

Question 7

What is phosphorescence?

Answer 7

Description: The process of producing light by the absorption of ultraviolet light resulting in the emission of visible light over an extended period of time
Examples: Glow in the dark toys, radium paint

Question 8

What is fluorescence?

Answer 8

Description: The immediate emission of visible light as a result of the absorption of ultraviolet light

Examples: Compact fluorescent lights, Uranium glass

Question 9

What is Chemiluminescence?

Answer 9

Description: The direct production of light as a result of a chemical reaction with little or no heat produced. When chemiluminescence occurs in living organisms, we call that bioluminescence

Examples: Glow sticks, fireflies, bioluminescent algae

Question 10

What is Triboluminescence?

Answer 10

Description: The production of light from friction as a result of scratching, crushing, or rubbing certain crystals

Examples: Rubbing quartz crystals, biting hard sugar candies

Question 11

What is Electroluminescence?

Answer 11

Description: The process of producing light when electrons and holes in a semiconductor recombine and release energy in the form of light

Examples: Light Emitting Diodes (LEDs)

Question 12

How do incandescent sources emit light?

Answer 12

→ Incandescent sources emit light of many different wavelengths and energy levels
→ Because it emits light at many different wavelengths all the colours blend together and we perceive it as white light

Question 13

How do lasers emit light?

Answer 13

→ Lasers emit electromagnetic waves of exactly the same energy level.
→ This produces a very pure colour.
→ The electromagnetic waves from a laser travel in exactly the same direction and are concentrated in a narrow, straight beam.
→ These properties make laser light very dangerous, and you should never look directly into a laser

Question 14

What is white light?

Answer 14

White light is a combination of all colors in the color spectrum. It has all the colors of the rainbow.

Question 15

What are light rays?

Answer 15

→ Luminous objects like candles radiate light in all directions this is why lighting a candle can illuminate a whole room
→ We illustrate the spread and motion of light using light rays
→ A light ray is a line and arrow representing the direction and straight-line path of light
→ While an infinite number of light rays come from the candle we only need to draw a few to represent the overall picture

Question 16

How do we use light rays and what does it determine? Explain the three conditions

Answer 16

→ We use light rays to help trace the path of light when it strikes an object
→ If all light passes straight through an object, we call that object transparent (e.g. glass,
or still water)
→ Objects that diffuse light as it passes through are called translucent (e.g. clear plastic,
frosted windows)
→ Objects that reflect or absorb almost all light are called opaque (e.g. paper, people,wood, most things)

Transparent: Light pass through completely
Translucent: light pass through partially
Opaque: No light pass through

Question 17

What are plane mirros made up of?

Answer 17

→ The first type of mirror we will discuss is a plane mirror (also known as a flat mirror)
→ The glass helps protect the thin film from scratches and dents as well as helping it keep its shape
→ The reflective film is typically made of silver or aluminum
→ Historically, mirrors were made of polished metals like bronze, silver or tin

Question 18

What is the normal?

Answer 18

the perpendicular line to a mirrors surface

Question 19

What is the incident ray?

Answer 19

the incoming ray that strikes a surface

Question 20

What is the angle of incidence?

Answer 20

the angle between the incident ray and the normal

Question 21

What is the reflected ray?

Answer 21

the ray that bounces off a reflective surface

Question 22

What is the angle of reflection?

Answer 22

the angle between the reflected ray and the normal

Question 23

What are the 2 laws of reflection?

Answer 23

→ When you shine an incident ray at a reflective surface, the light is always reflected off the mirror in a predictable way
→ This predictable behaviour leads to the two laws of reflection:

The angle of incidence equals the angle of reflection.

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

Question 24

What happens when multiple rays are reflected off a surface?

Answer 24

→ When multiple rays are reflected off a surface, each ray obeys the laws of reflection.
→ Therefore, we can consider what happens to a whole image by imagining each point emitting a ray towards the viewer.

Question 25

What is a specular reflection?

Answer 25

→ Specular reflection is the reflection of light off a smooth, shiny surface. → Because the surface is flat, any rays that are parallel coming into the mirror will stay parallel after being reflected. This is why you get a clear image. → Examples include reflections off: Mirrors, very still water, a flat piece of aluminum, disco ball

Question 26

What are diffuse reflections?

Answer 26

→ Diffuse reflection is the reflection of light off an irregular or dull surface. → Here, our parallel incident rays are reflected, or scattered, in many different directions. This causes a blurry or softened image (if there is one at all!) → Examples include reflections off: Paper, turbulent water, crumpled aluminum foil

Question 27

What is a virtual image and how does our mind perceive it?

Answer 27

→ Millions of light rays are being reflected off the objects around us, but we are only concerned with the ones that are being reflected into our eyes → Your brain projects these light rays backwards through the mirror in a straight line → This resulsts in our brain thinking the light source is behind the mirror → There is no light source heind the mirror because the mirror is opaque → This kind of image is called a virtual image → A virtual image is an image formed by light coming from an apparent light source, light is not arriving at or coming from the actual image location it only appears to come from the image location

Question 28

What helps us see how a plane mirror produces a virtual image and where it is located? What does this process allow us to see?

Answer 28

→ Using light rays and the laws of reflection helps us see how a plane mirror produces a virtual image and where it is located → This process allows us to see The distance between teh object and the mirror is exactly the same as the distance between teh mirror and the image The object-image line is perpendicular to the mirrors surface

Question 29

What methods are used to observe the virtual image created?

Answer 29

Ray method and equal-perpindicular lines

Question 30

How are the characterstics in a plane mirror?

Answer 30

→ An image in a plane mirror is upright but flipped horizontally compared to the object → The order of letters are also reversed → This is called lateral inversion → In a plane mirror, the image is always the same size, upright but laterally inverted, behind the mirror, the same distance behind as the object is in front and virtual

Question 31

What are the four characteristics of describing properties?

Answer 31

→ You need to examine four characteristics when describing properties of an image: size, orientation, location and type

Question 32

Explain SALT

Answer 32

→ Size: the size of image compared to the object (ex. Same size, smaller or larger) → Attitude: the orientation of the image compared to the object (ex. Upright or inverted) → Location: where teh image is located relative to the mirror (ex. In front, behind, distance) → Type: the type of image produced (ex. Real or virtual)

Question 33

How do the electromagnetic waves transfer energy?

Answer 33

Electromagnetic waves transfer energy through their electric and magnetic fields, which oscillate at right angles to each other. These oscillating fields carry energy, and the strength of the fields determines the amount of energy transferred. This transfer of energy is called electromagnetic radiation Electromagnetic waves are disturbances in both electric and magnetic fields. These fields are not just static; they are constantly changing and oscillating. The oscillating electric and magnetic fields couple together, and this coupling allows the wave to carry energy across space or through matter. When electromagnetic waves interact with matter, they can be absorbed, reflected, or transmitted. The energy of the wave is then converted into other forms of energy, such as heat or kinetic energy, or it can be used to move charges within the material.

Question 34

What is the center of curvature?

Answer 34

The center of the sphere whose surface has been used to make the mirror

Question 35

What is the principal axis?

Answer 35

the lines through the center of curvature to the midpoint of the mirror

Question 36

What is the vertex?

Answer 36

The point where the principal axis meets the mirror

Question 37

What is the focus point?

Answer 37

the point where reflected rays from parallel incident rays pass through or converge

Question 38

Why are concave mirrors called converging mirrors?

Answer 38

Concave mirrors are also called converging mirrors since the rays of light converge when it strikes the mirror's surface. The point where the parallel rays converge is the focal point.

Question 39

How do you locate the image in a concave mirror?

Answer 39

A ray parallel to the principal axis is reflected through the focus A ray through the center of curvature is reflected back onto itself A ray through the focus will reflect parallel to the principal axis A ray aimed at the vertex will follow the law of reflection

Question 40

What is a real image?

Answer 40

→ A real image is any image that can be seen on a screen because light rays are actually arriving at the image location

Question 41

What devices use concave mirrors?

Answer 41

→ Flashlights and searchlights use concave mirrors with the light source placed at the focus → By the reversibility of light, any light coming from the focus will reflect in parallel lines, this allows us to focus the light in a straight beam → The opposite of this is used in telescope and satellite dishes → Electromagnetic waves come in parallel rays and are reflected onto the focal point where they are collected and processed

Question 42

How do you locate the image in a convex mirror?

Answer 42

A ray parallel to the principal axis is reflected as if it had come from the focus A ray through the center of curvature is reflected back onto itself A ray aimed at the focus will reflect parallel to the principal axis

Question 43

Why are convex mirrors called diverging mirrors?

Answer 43

→ The reflected rays off a convex mirror never converge hence why they are sometimes called diverging mirrors Convex mirrors are called diverging mirrors because the light rays that reflect off their surface spread out (diverge) after being reflected.

Question 44

Why are convex mirrors useful?

Answer 44

→ Since the virtual images produced are smaller and upright, convex mirrors are very useful as security mirrors → Convex mirrors are also used as side-view mirrors on vehicles so that is why is says “Objects in mirror are closer than they appear” to remind that they are seeing a smaller image

Question 45

What are the properties and where is the image located when object is beyond C?

Answer 45

→ Beyond C (smaller, vertically inverted, between C & F, real)

Question 46

What are the properties and where is the image located when object is at C?

Answer 46

→ At C (same, vertical inversion, at C, real)

Question 47

What are the properties and where is the image located when object is between C and F?

Answer 47

→ Between C and F (larger, vertical inversion, beyond C, real)

Question 48

What are the properties and where is the image located when object is at F? Why?

Answer 48

→ At F (No clear image) When an object is placed at the focal point of a concave mirror, no clear image is formed because the reflected light rays are parallel. This means they do not converge or diverge in a way that would allow the formation of an image, real or virtual.

Question 49

What are the properties and where is the image located when object is between F and V?

Answer 49

→ Between F and V (larger, upright and horizontally inverted, other side of mirror, virtual)

Question 50

What are the properties and where is the image located when object is beyond V?

Answer 50

→ Beyond V (smaller, upright, between V + F, virtual)

Question 51

What is the difference between convex and concave mirrors?

Answer 51

Concave mirrors curve inward, reflecting light towards a focal point, while convex mirrors curve outward, reflecting light away from a focal point. This difference leads to distinct image formation and application characteristics for each type of mirror. diminished images form in convex mirrors while enlarged images form in concave mirrors.

Question 52

What is the relationship between the type and the attitude of an image?

Answer 52

The attitude of the image depends on the type of the image. Real images are always inverted while virtual images are always upright.

Question 53

What is the difference between a real image and a virtual image?

Answer 53

Real images are formed on a screen (this screen may be a screen, a prjector screen or the retina of the eye). These are formed by the actual intersection of light rays. Virtual images are not formed on a screen and are not formed by the actual intersection of light rays, but a point where the brain and the eye imagines the reflected light from the object to be coming from

Question 54

Why is diffuse reflection better in a classroom?

Answer 54

In a classroom, diffuse reflection is desirable for the walls. This is because it allows light to scatter in many directions, making the room appear brighter and more even, while also preventing harsh glare and excessive reflection. Specular reflection, which occurs on smooth, shiny surfaces like mirrors, would cause a glare and make it difficult to see clearly.

Question 55

Classify each of these materials as transparent translucent, or opaque: a textbook, frosted glass, a single sheet of tissue paper, a clean sheet of glass, a rock, clean air, apple juice, sunglasses.

Answer 55

- A textbook is opaque - A frosted glass is translucent - A single sheet of thin tissue paper is translucent - A clean sheet of glass is transparent - A rock is opaque - Clean air is transparent - Apple juice is translucent - Sunglasses are transparent

Question 56

What is geometric optics?

Answer 56

Geometrical optics is a term used to represent ray diagrams in a figure

Question 57

Do fluorescent brighters in detergents really make clothes cleaner?

Answer 57

Fluorescent brighteners in detergents do not make the clothes cleaner, these on clothes absorb ultraviolet light and emit visible light so to the eye, the clothes appear brighter and therefore look cleaner.