Chapter 1: Electromagnetic waves

Question 1

Chapter 1: A

Define a “wave.”

Answer 1

A wave is defined as the net transfer of energy (via oscillations) from one location to another without the net transfer of matter.

Question 2

Chapter 1: A

Define a transverse wave

Answer 2

A transverse wave is a transmission of energy where particles oscillate perpendicularly to the direction in which the wave propagates.

Question 3

Chapter 1: A

Define a longitudinal wave

Answer 3

A longitudinal wave transmits energy where particles oscillate parallel to the direction in which the wave propagates.

The oscillations of a longitudinal are also referred to as compression’s.

Question 4

Chapter 1: A

Define an electromagnetic wave

Answer 4

An electromagnetic wave is a wave created due to the perpendicular oscillations of an electric and magnetic field. Hence, being classified as a transverse wave.

All wavelengths of electromagnetic radiation travel at a constant speed of 3 x 10^8 meters per second in a vacuum.

Question 5

Chapter 1: A

Define a vacuum

Answer 5

A vacuum (in physics) is defined as a region or location which occupies no matter.

Question 6

Chapter 1: A

Define a mechanical wave

Answer 6

A mechanical wave is created via the oscillations of particles (or matter) within a specific medium.

Mechanical waves can be either longitudinal or transverse.

Question 7

Chapter 1: A

Define a medium

Answer 7

A medium (in the context of waves) is defined as any physical substance in which a wave can propagate through.

Question 8

Chapter 1: B

Define a wave cycle

Answer 8

A wave cycle is defined as the process of a wave completing one full oscillation, with the wave ending up in a configuration identical to its initial configuration.

Question 9

Chapter 1: B

Define the property of “amplitude.”

Answer 9

The amplitude of a wave refers to the maximum displacement of a particle (from a wave’s neutral point) which oscillates a wave.

Symbol A:

Question 10

Chapter 1: B

Define the term “crest.”

Answer 10

The crest refers to the maximum positive displacement of a particle that oscillates a wave.

Question 11

Chapter 1: B

Define the term “trough.”

Answer 11

The trough refers to the maximum negative displacement of a particle that oscillates a wave.

Question 12

Chapter 1: B

Define the property of “wavelength.”

Answer 12

This term refers to the distance covered (in meters) of one complete wave cycle.

Symbol-L shaped

Question 13

Chapter 1: B

Define the property “frequency.”

Answer 13

The frequency of a wave refers to the number of wave cycles completed per unit of time.
Expressed in HZ.

Symbol-F

Question 14

Chapter 1: B

Define the property of “period.”

Answer 14

The period of a wave refers to the time taken (in seconds) to complete one full wave cycle.

Symbol-T

Question 15

Chapter 1: B

Distinguish between a displacement/distance graph and a displacement/time graph.

Answer 15

A displacement/distance graph pauses a wave at a particular point in time. It can be used to dictate the amplitude and wavelength of a wave.

A displacement/time graph observes the movement of a certain particle oscillating a wave over time. It can be used to dictate the amplitude, period, and frequency of a wave.

Question 16

Chapter 1: B

Describe how the source of a wave impacts its frequency and period.

Answer 16

The source of a wave refers to the matter or particles oscillating in that wave.

The faster the particles or matter oscillate of a wave, the greater the corresponding frequency will be. Due to the inverse relationship, a higher frequency will yield a lower period for that wave.

Question 17

Chapter 1:c

Define the electromagnetic spectrum

Answer 17

The Electromagnetic spectrum (EM) comprises all the varying forms of electromagnetic radiation based on their frequencies and wavelengths.

The spectrum is ordered by increasing frequencies (and energies) and decreasing wavelengths.

Question 18

Chapter 1:c

List the order of the EM spectrum.

Answer 18

Radio waves-
Microwaves-
Infrared-
Visible light-
Ultraviolet-
X rays-
Gamma rays-

Question 19

Chapter 1:c

List the proportions of EM regions emitted via the sun

Answer 19

The sun emits the following proportions of electromagnetic radiation.

50% infrared-40% visible light-10% Ultraviolet

Question 20

Chapter 1:c

List the frequencies of the visible spectrum in order of decreasing wavelengths.

Answer 20

Red-Orange-Yellow-Green-Blue-Indigo-Violate.

Question 21

Chapter 1:c

Describe the use of Radio waves in society

Answer 21

Given Radio waves have the longest wavelengths across all regions on the EM spectrum these rays can travel long and uninterrupted distances, diffracting around large objects.

This form of EM radiation is used commonly in communication settings. As radio waves are emitted via towers and can be picked up by antennas.

Question 22

Chapter 1:c

Describe the use of micro-waves in society

Answer 22

Given microwaves also comprise significant wavelengths with shorter frequencies they are utilized in society regarding radar/WiFi systems and phone signals, as these rays can travel long distances. Microwaves can also be used to heat food as well.

Question 23

Chapter 1:c

Describe the use of infrared rays in society

Answer 23

All objects with a temperature greater than 0 K will emit infrared radiation due to the kinetic energy of particles.

Infrared is used in various activities that involve heat/heat transmissions. Including radiation heaters which convert infrared radiation to different objects in an area, causing them to heat up.

Question 24

Chapter 1:c

Describe the use of visible light in society.

Answer 24

Visible light allows humans to perceive color. When a human sees a color it’s a frequency of the visible spectrum, being reflected off an object with the remaining frequencies absorbed by that object.

Question 25

Chapter 1:c

Describe the use of Ultraviolet rays in society

Answer 25

Ultraviolet radiation is found on the higher frequency/energy half of the EM spectrum.

Due to this higher energy, it’s often used to harden certain products (sterilization).

Ultraviolet rays are also used in forensics as they can cause objects to emit visible light.

Question 26

Chapter 1:c

Describe the use of X-rays in society

Answer 26

X-rays have a large amount of energy due to greater frequency levels.

Due to these large amounts of energy, they are penetrating, making them useful for taking images of bones and killing or damaging human cells.

Question 27

Chapter 1:c

Describe the use of gamma-rays in society

Answer 27

Gamma rays have the highest frequencies (and energy levels) across all radiation forms across the EM spectrum.

Therefore, due to these extremely high levels of energy, they are penetrating and can be used to target or kill tumor cells in a human.

Question 28

Chapter 1:D

Define the “Normal.”

Answer 28

The normal is an imaginary line situated perpendicularly to a light ray approaching a boundary between two mediums.

Question 29

Chapter 1:D

Define the angle of incidence

Answer 29

The angle of incidence is the angle a light ray makes to the normal when approaching a boundary between two mediums.

Question 30

Chapter 1:D

Define the angle of reflection

Answer 30

The angle of reflection is the angle to the normal at which the ray is reflected (bounced back) from the boundary between two mediums.

Note: The angle of reflection will always equal the angle of incidence.

Question 31

Chapter 1:D

Define the angle of refraction

Answer 31

The angle of refraction is the angle at which a light ray is refracted (a change in direction in medium 2) from the normal at the boundary between two mediums.

Question 32

Chapter 1:D

Define the refracitve index

Answer 32

The refractive index is defined as the ratio of light’s speed in a vacuum (3 x 10^8 meters per second) to light’s speed in a given medium.

Question 33

Chapter 1:D

Define the critical angle

Answer 33

The angle of incidence at which the ray will be refracted at exactly 90 degrees.

Any incident angle greater than this critical angle will not transmit to a second medium, known as total internal reflection.

Question 34

Chapter 1:D

Define total internal reflection

Answer 34

Total internal reflection occurs when light cannot be transmitted from one medium to another and can only be reflected.

Total internal reflection only occurs if the angle of incidence is greater than the critical angle for two given mediums.

Question 35

Chapter 1:E

Define White light

Answer 35

White light is the combination of all the different frequencies of the visible spectrum.

Question 36

Chapter 1:E

Define dispersion

Answer 36

Dispersion is defined as the separation of white light’s frequencies when it enters a certain medium.

Dispersion occurs as the different frequencies of the visible spectrum form different speeds (corresponding to different refractive indices) in given mediums. Hence, different refracted angles of white light’s frequencies in a medium are seen which causes them to separate.

Question 37

Chapter 1:E

Explain the formation of a rainbow

Answer 37

A rainbow is an application of dispersion, as it occurs when white light enters water droplets in the air and the different frequencies of the visible spectrum refract at different angles.

The reflected rays from a water droplet travel to the eyes of an observer (provided they are a sufficient distance away). Each water droplet reflects one frequency (color) into an observer’s eye, depending on where an observer is standing.

Therefore, the combination of millions of water droplets causes all frequencies of visible light to be reflected into an observer’s eyes, causing them to perceive a rainbow.

Question 38

Chapter 1:E

Define a mirage

Answer 38

A mirage is an optical illusion that occurs when light rays travel through the air which has ranging temperatures.

Which causes light to refract in different regions of the air, eventually refracted towards an observer’s eye. This is where the mirage occurs as the human brain assumes that light travels in a straight line.

Question 39

Chapter 1:E

Define an inferior mirage

Answer 39

A mirage occurring when the temperature of the air decreases with height. Where temperature increases as the light ray approaches the ground.

This mirage will occur on the surface of the earth.

Question 40

Chapter 1:E

Define a superior mirage

Answer 40

A mirage occurs when the temperature of the air increases with height.

This mirage will occur above an observer in the sky.

Question 41

Chapter 1:E

Define an Optical Fibre

Answer 41

An optical fibre is a glass tube that utilizes total internal reflection to transmit light from one location to another.

Question 42

Chapter 1:E

Define the “layer of cladding enclosing an optical fibre.”

Answer 42

This layer of cladding is a material that protects an optical fibre from its external environment and has a lower refractive index than the optical fibre it encloses. Which makes total internal reflection possible.

Question 43

Chapter 1:E

Define a fibre-optic cable

Answer 43

A fiber-optic cable is a cable that contains multiple optical fibers enclosed by a layer of cladding. What this does is it transmits light across lengthy distances.

For instance, these cables are found often on the ocean floor. As they can transfer data across lengthy distances.