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Science 8 > Light and Optics Unit Exam > Flashcards

Light and Optics Unit Exam Flashcards

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1
Q

If you see the colour purple, what colour is being reflected?

A

Purple.

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2
Q

What did Pythogoras do?

A

He thought that humans could see by shooting light out of our eyes like a laser beam. Problem was, we couldn’t see in the dark lmao

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3
Q

What did Euclid do?

A

He discovered that light travels in straight lines. He also came up with the Law of Reflection.

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4
Q

What did Ptolemy do?

A

He discovered that light bends as it passes from air to glass.

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5
Q

What did al-Haytham do?

A

First person to accurately describe how vision worked — Light bounces off objects then travels to the eye.

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6
Q

What did Newton do?

A

Used a prism to show that white light is a mix of all the colours

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7
Q

Name 4 basic properties of light.

A
  1. Light travels in straight lines
  2. Light can be reflected
  3. Light can bend
  4. Light is a form of energy
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8
Q

What is an optical device? Give 3 examples.

A

Any device that uses light.

Ex. Glasses, eyes, mirror

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9
Q

What is a microscope?

A

An optical device used to looking at tiny things. It must have at least 2 lenses.

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10
Q

What are the 2 lenses of a microscope called?

A

The objective lens and the eyepiece lens.

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11
Q

Who is Antonie van Leeuwenhoek?

A

The first person to identify micro-organisms. Also, he created a more powerful and useful design for the microscope.

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12
Q

How does a microscope work?

A

The image is magnified through the lenses, and bends light toward the eye and makes an object appear larger than it actually is.

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13
Q

What is a telescope?

A

An optical device used for viewing objects far away.

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14
Q

What are the two types of telescopes?

A

Reflecting telescope (more complicated) and refracting telescope (less complicated).

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15
Q

Name 2 things telescopes use mirrors and lenses to do.

A
  1. Magnify

2. Collect Light

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16
Q

How does a refracting telescope work?

A

It uses 2 lenses to form an enlarged image.
Starlight enters through the end of the telescope and into the first lens, which bends the light so it hits the second lens a certain way. It then goes through the second lens (the eyepiece) and into your eye.
Draw it.

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17
Q

How does a reflecting telescope work?

A

It uses curved mirrors and a lens to form an enlarged image.
Starlight enters through the end of the telescope and hits the Primary Mirror on the other end. That mirror then reflects the light so that it hits the Secondary Mirror (suspended around the middle-end of the telescope). The Secondary Mirror then reflects the light into the eyepiece where it hits your eye.
Draw it.

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18
Q

What are binoculars?

A

Two small refracting telescopes put together. Smaller, easier to move, and more convenient than a big telescope.

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19
Q

What is a ray diagram?

A

Diagram used to represent how light travels. Each ray has a straight arrow to show the direction where the ray is going.

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20
Q

Describe intensity.

A

The brightness of light. The amount of light arriving per unit unit area at a place.
The further the light source, the lower intensity; fewer light rays reach your eyes.

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21
Q

How do shadows work?

A

Light rays come from the point source, and based on on how far the object is from the point source, you can see how many rays are blocked. The closer it it, the more rays it blocks, and the bigger the shadow will be. The further it is, the less rays it will block, so the shadow will be smaller. Also, the angle of where the point source is alters the shape of the shadow.

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22
Q

What is transparent? Give 2 examples.

A

Lets light through with little or no reflection.

Ex. Glass, a ziplock bag.

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23
Q

What is translucent? Give 2 examples.

A

Lets some light through.

Ex. Frosted window, the squiggly glass at the RGC change room.

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24
Q

What is opaque? Give 2 examples.

A

Lets no light through.

Ex. Wood, human.

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25
Q

What is luminous? Give 2 examples.

A

Thing that produces light.

Ex. Sun, Will Solace (when he chooses)

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26
Q

What is non-luminous? Give 2 examples.

A

Thing that does NOT produce light, but CAN reflect it.

Ex. Non-magical book, desk.

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27
Q

What are the 2 types of reflection?

A

Regular reflection and diffuse reflection.

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28
Q

What is regular reflection?

A

Reflection that happens when parallel rays hit a smooth surface. All rays reflect at the same angle.

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29
Q

What is diffuse reflection?

A

Reflection that happens when parallel rays hit a rough surface. All rays reflect at different angles.
Ex. Water

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30
Q

What are Incident Rays?

A

Ray of light that arrives at a mirror or other substance (the shinier and smoother the surface the better the reflection).

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31
Q

What are Reflected Rays?

A

Ray of light that bounces off a mirror or another substance.

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32
Q

What is the Normal Line?

A

Line sticking off the surface at a 90 degree angle.

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33
Q

What is the Angle of Incidence?

A

Angle between the Normal and the Incident Ray.

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34
Q

What is the Angle of Reflection?

A

Angle between the Normal and the Reflected Ray.

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35
Q

What is the Law of Reflection?

A

Angle of Incidence of a wave hitting a surface equals the angle of reflection. ALL surfaces obey this law.

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36
Q

What is a concave mirror?

A

Mirror that is curved inward like a bowl or spoon.

Ex. Reflecting telescope, car headlights.

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37
Q

How does a concave mirror reflect?

A

Light rays reflected converge — come together.

38
Q

“Image from a concave mirror depends on the…”

A

Distance from the focal point.

Recite the quote.

39
Q

What is a focal point?

A

Point at which light rays meet, or appear to meet, after being reflected by a mirror, or refracted by a lens.

40
Q

If the object is far from the focal point, how will the image look?

A

Upside down, smaller.

41
Q

If the object is closer to the focal point, how will the image look?

A

Upside down, larger.

42
Q

If the object is on the focal point, how will the image look?

A

There will be no image.

43
Q

If the object is between the focal point and the mirror, how will the image look?

A

Upright, enlarged.

44
Q

What is a convex mirror?

A

Mirror that bulges out like the back of a spoon.

45
Q

How does a convex mirror reflect?

A

Light rays reflected diverge — spread out.

46
Q

“The image appears like it is originating…”

A

From a smaller point behind the mirror. Useful for side mirrors.

47
Q

What happens when a light ray strikes a boundary where two different substances meet at an angle?

A

It will change direction.

48
Q

“Human eyes assume the light rays move through the boundary in a straight line so we…”

Hint: Hatchet

A

Incorrectly identify where the object is in the other substance.

49
Q

What is refraction?

A

The bending of light as it travels from one medium to another.

50
Q

Why does refraction occur?

A

Because the speed of light changes in different substances.

51
Q

What is the speed of light in space?

A

300 000 km/second.

52
Q

“The denser the new medium…”

A

The more the light slows down and refracts.

53
Q

Name two things lens ability depends on.

A
  1. Shape of lens.

2. Material of the lens.

54
Q

What is a lens?

A

Curved piece of glass that other transparent material that refracts light in a predictable way. Useful because the light rays that refract can form images.

55
Q

What is a concave lens?

A

Thinner in the middle than at the edges.

56
Q

How does a concave lens refract?

A

Light rays diverge — spread out.

Opposite of concave mirror!

57
Q

What is a convex lens?

A

Thicker in the middle than at the edges.

58
Q

How does a convex lens refract?

A

Light rays converge — come together.

Opposite of convex mirror!

59
Q

What is a double convex lens?

A

A lens that curves out on both sides.

60
Q

“Light rays refracted through a convex lens…”

A

Meet at a focal point.

61
Q

List 2 reasons convex lenses are useful.

A
  1. Good light collector.
    Ex. Refracting telescope
  2. Forms a real image.
62
Q

What is a real image?

A

An image that looks like a real object — not distorted.

63
Q

“Main drawback is that the image produced…”

A

Is upside down.

64
Q

L If the object is far from the focal point, how will the image look?

A

Upside down, smaller, real image.

65
Q

L If the object is closer to the focal point, how will the image look?

A

Upside down, larger, real image.

66
Q

L If the object is on the focal point, how will the image look?

A

There will be no image.

67
Q

L If the object is between the focal point and the lens, how will the image look?

A

Upright, enlarged, same side as object.

68
Q

What is the cornea? What does it do?

A

The cornea is a clear substance on the outside of the eye, protecting the iris and the pupil.

69
Q

What is the iris? What does it do?

A

The iris is the coloured part of your eye, and is a muscle. It controls how much light is let into your eye through your pupil.

70
Q

What is the pupil? What does it do?

A

The pupil is the black dot in the middle of your eye. It’s actually a hole that lets light into your eye. It’s controlled my the iris.

71
Q

What are ciliary muscles? What do they do?

A

Ciliary muscles are muscles that hold the lens in place, and change its shape when they have too.

72
Q

What is the lens? What does it do?

A

The lens is a lens (obviously lol) that has a football-like shape. It focuses the light that enters your eye onto the retina. The image produced by it is actually upside down, but its ok because your brain fixes it.

73
Q

What is the retina? What does it do?

A

Your retina is a turquoise-iridescent thing that is at the back of your eye. It reads the light from the lens. It has 2 types of photoreceptors, called Rods and Cones, which interpret the image.

74
Q

What are Rods? What do they do?

A

Rods are a photoreceptor in your retina, and are very sensitive to dim light.

75
Q

What are Cones? What do they do?

A

Cones are a photoreceptor in your retina, and are very sensitive to bright lights, and read colours.
Cones cant function in low light, so we only see greys in dim lighting.

76
Q

What happens when photoreceptors are stimulated?

A

They send a message (the image) to the brain through the optic nerve, where it will be read and interpreted.

77
Q

How are the camera and your eye related?

A

Pupil — aperture
Iris — diaphragm
Retina — film
Lens — lens

78
Q

What is nearsightedness?

A

When you cant see far away.
The eye cant make the lens thin enough to focus the light on the retina, so a concave lens is used to converge the light onto the retina

79
Q

What is farsightedness?

A

When you cant see near.
The eye cant make the lens thick enough to focus the light onto the retina, so a convex lens is used to diverge the light onto the lens.

80
Q

How does laser eye surgery work?

A

The lens in your eye is reshaped by a laser.

81
Q

What are compound eyes?

A

On insects and crustaceans.
Made up of many individual units called ommatidium.
These eyes are great for detecting movement, but not for creating a single coherent image.

82
Q

“The brain sends and receives signals as…”

A

Electrical impulses traveling across neurons

83
Q

T/F: scientists understand how these images are stored.

A

False.

84
Q

If you take any form of information and convert it into numbers, is it digital?

A

Yes. Always.

85
Q

What is a “stadium image”?

A

The process of creating a big picture out of small pieces, like ones created in a stadium, which is similar to the process of digital imaging.

86
Q

What happens when a computer receives an image?

A

Breaks it up into pixels.

87
Q

How does it colour a digital image?

A

The computer assigns a value to each pixel which corresponds to a certain colour.
Ex. 221 is light purple

88
Q

Define resolution.

A

The quality of an image.

89
Q

Is an image with lots of small pixels better than an image with a couple of big ones?

A

Yes.

90
Q

How is an image captured on a digital camera?

A

The light falls onto a charge-coupled device (CCD), which is a grid similar to a piece of graph paper.

91
Q

Name 2 advantages of digital images.

A
  1. It can easily be sent great distances.

2. It can collect other parts of the electromagnetic spectrum.

Science 8 (3 decks)

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