Unit 9-10

Question 1

Light

Answer 1

A form of energy that travels as an electromagnetic wave.

Question 2

Luminous object

Answer 2

An object that produces its own light.

Question 3

Examples of luminous objects

Answer 3

Sun (nuclear), flashlight (electrical), match (chemical).

Question 4

Non-luminous object

Answer 4

An object that does not produce its own light but reflects light.

Question 5

Examples of non-luminous objects

Answer 5

Moon, tree.

Question 6

Incandescence

Answer 6

Light produced by an object due to very high temperature (e.g., filament in a bulb).

Question 7

Electric discharge

Answer 7

Light produced when electricity passes through gas (e.g., neon lights, lightning).

Question 8

Phosphorescence

Answer 8

Light released slowly after absorbing energy (e.g., glow-in-the-dark materials).

Question 9

Fluorescence

Answer 9

Light emitted when a substance absorbs electromagnetic radiation (e.g., fluorescent bulbs).

Question 10

Chemiluminescence

Answer 10

Light produced from a chemical reaction without heat (e.g., glow sticks, luminol).

Question 11

Bioluminescence

Answer 11

Light produced by living organisms (e.g., fireflies).

Question 12

Triboluminescence

Answer 12

Light produced by friction or crushing (e.g., crystals, sugar).

Question 13

LED

Answer 13

Light produced by electrons moving in a semiconductor.

Question 14

OLED

Answer 14

Thin organic layers that emit light when electric current passes through them.

Question 15

Plasma display

Answer 15

Produces light using electric discharge in gas and phosphors.

Question 16

LCD

Answer 16

Does not produce light; controls light from a backlight.

Question 17

Electromagnetic waves

Answer 17

Radio waves, microwaves, visible light, X-rays, gamma rays.

Question 18

Main difference in electromagnetic waves

Answer 18

Wavelength (which determines energy).

Question 19

Speed of light symbol

Answer 19

c

Question 20

Speed of light in vacuum

Answer 20

3.0 × 10⁸ m/s (300,000,000 m/s).

Question 21

Medium

Answer 21

A physical substance that carries energy (e.g., air, water).

Question 22

How light travels through space

Answer 22

By radiation; does not require a medium.

Question 23

Wave

Answer 23

A disturbance that transfers energy without transferring matter.

Question 24

Crest

Answer 24

Highest point of a wave.

Question 25

Trough

Answer 25

Lowest point of a wave.

Question 26

Wavelength

Answer 26

Distance between two identical points on a wave (crest to crest or trough to trough).

Question 27

Amplitude

Answer 27

Height of a wave from rest position to crest or trough.

Question 28

Frequency

Answer 28

Number of wave cycles per second.

Question 29

Relationship between frequency and wavelength

Answer 29

Inverse relationship (as one increases, the other decreases).

Question 30

Electromagnetic spectrum

Answer 30

All types of electromagnetic radiation arranged by wavelength.

Question 31

Long wavelengths

Answer 31

Radio waves, microwaves.

Question 32

Short wavelengths

Answer 32

X-rays, gamma rays.

Question 33

Visible light

Answer 33

The only part of the electromagnetic spectrum humans can see.

Question 34

Short wavelength energy

Answer 34

Higher energy and higher frequency.

Question 35

Order of visible spectrum

Answer 35

Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV).

Question 36

Red light wavelength

Answer 36

~700 nm.

Question 37

Violet light wavelength

Answer 37

~400 nm.

Question 38

Additive colour theory

Answer 38

White light is made of different colours of light.

Question 39

Subtractive colour theory

Answer 39

Materials absorb certain wavelengths and reflect others.

Question 40

Reflection

Answer 40

Light bouncing off a surface.

Question 41

Refraction

Answer 41

Bending of light when it passes between media.

Question 42

Diffraction

Answer 42

Light spreading out around edges or openings.

Question 43

Interference

Answer 43

Overlapping waves forming bright and dark patterns.

Question 44

Polarization

Answer 44

Light waves vibrating in specific directions.

Question 45

Transparent material

Answer 45

Lets most light pass through.

Question 46

Translucent material

Answer 46

Lets some light pass but not clearly.

Question 47

Opaque material

Answer 47

Does not let light pass through.

Question 48

Shadow

Answer 48

Formed when an opaque object blocks light.

Question 49

Umbra

Answer 49

Darkest part of a shadow where all light is blocked.

Question 50

Penumbra

Answer 50

Partial shadow where some light is blocked.

Question 51

Regular reflection

Answer 51

Light reflects off smooth surface; rays remain parallel.

Question 52

Diffuse reflection

Answer 52

Light reflects off rough surface; rays scatter.

Question 53

Law of reflection

Answer 53

Angle of incidence equals angle of reflection.

Question 54

Normal

Answer 54

Imaginary line perpendicular to surface at point of contact.

Question 55

Incident ray

Answer 55

Incoming light ray.

Question 56

Reflected ray

Answer 56

Bounced light ray.

Question 57

Plane mirror

Answer 57

Flat reflective surface.

Question 58

Image in plane mirror

Answer 58

Upright, same size, laterally inverted, virtual.

Question 59

Virtual image

Answer 59

Image formed where light rays only appear to meet.

Question 60

Real image

Answer 60

Image formed where light rays actually meet; can be projected on a screen.

Question 61

SALT

Answer 61

Size, Attitude, Location, Type (describes images).

Question 62

Magnification (by height)

Answer 62

Image height ÷ object height.

Question 63

Magnification (by distance)

Answer 63

Image distance ÷ object distance.

Question 64

Concave mirror

Answer 64

Inward curved mirror; converges light rays.

Question 65

Convex mirror

Answer 65

Outward curved mirror; diverges light rays.

Question 66

Concave mirror image

Answer 66

Can be real (inverted) when far or virtual (upright) when near depending on distance.

Question 67

Convex mirror image

Answer 67

Always virtual, upright, smaller.

Question 68

Centre of curvature (C)

Answer 68

Center of the sphere forming the mirror.

Question 69

Vertex (V)

Answer 69

Point where principal axis meets mirror.

Question 70

Principal axis

Answer 70

Line through C and V.

Question 71

Focal point (F)

Answer 71

Point where parallel rays converge (concave) or appear to diverge from (convex).

Question 72

Focal length (f)

Answer 72

Distance from focal point to vertex.

Question 73

Refraction

Answer 73

Bending of light due to speed change between media.

Question 74

Refracted ray

Answer 74

Ray that bends in new medium.

Question 75

Angle of refraction

Answer 75

Angle between refracted ray and normal.

Question 76

Light entering denser medium

Answer 76

Bends toward the normal.

Question 77

Light entering less dense medium

Answer 77

Bends away from the normal.

Question 78

Index of refraction (n)

Answer 78

Ratio of speed of light in vacuum to speed in medium (n = c/v).

Question 79

Refractive index of vacuum

Answer 79

1.00

Question 80

Higher refractive index means

Answer 80

Greater optical density and slower light speed.

Question 81

Optical density

Answer 81

Ability of a medium to slow light.

Question 82

Snell’s Law

Answer 82

n₁sinθ₁ = n₂sinθ₂

Question 83

When does refraction occur?

Answer 83

Only at the boundary between two media.

Question 84

Critical angle

Answer 84

The angle of incidence in a denser medium that causes the refracted ray to bend 90° along the boundary.

Question 85

Total internal reflection

Answer 85

Complete reflection of light within a medium when the incident angle exceeds the critical angle.