2C3 Waves and Optics

Question 1

What is light?

Answer 1

A form of electromagnetic radiation with oscillating electric and magnetic fields.

Light behaves both as a wave and as particles (photons), depending on the context.

Question 2

What are the two components of light waves?

Answer 2

• Electric fields
• Magnetic fields

These fields oscillate perpendicularly to each other and to the direction of wave propagation.

Question 3

What is the speed of light in a vacuum?

Answer 3

Approximately 3.00 × 10⁸ m/s.

This value is equivalent 186,000 mi/s. This speed is a fundamental constant in physics, denoted by the symbol c.

Question 4

True or False:

Light requires a medium to propagate.

Answer 4

False

Unlike sound waves, which need a material medium (air, water, or solids), light can travel through the vacuum of space due to its oscillating electric and magnetic fields, which sustain each other.

Question 5

Fill in the blank:

______ exhibits both wave and particle properties.

Answer 5

Light

This duality is a cornerstone of quantum mechanics.

Question 6

What is a photon?

Answer 6

A quantum, or particle, of light energy.

They are massless particles that carry energy proportional to their frequency.

Question 7

What is a wavelength?

Answer 7

The distance between two consecutive peaks or troughs of a wave.

Wavelength is typically denoted by the symbol λ (lambda) and is measured in units of length, such as meters or nanometers.

Question 8

What equation relates the energy of a photon to its frequency?

Answer 8

E = h x f

Here, E is energy, h is Planck’s constant (6.26x10^-34^), and f is the frequency.

Question 9

What is the visible spectrum?

Answer 9

The portion of the electromagnetic spectrum visible to the human eye.

It ranges from approximately 380 nm (violet) to 700 nm (red).

Question 10

True or False:

The electromagnetic spectrum includes only visible light.

Answer 10

False

It includes gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves.

Question 11

What determines the color of visible light?

Answer 11

The wavelength of the light.

Shorter wavelengths correspond to violet and blue, while longer wavelengths correspond to red.

Question 12

Fill in the blank:

The ________ spectrum encompasses all types of electromagnetic radiation.

Answer 12

electromagnetic

The electromagnetic spectrum includes all forms of electromagnetic radiation, classified by their wavelength and frequency, from low-energy radio waves to high-energy gamma rays.

Question 13

What is the order of colors in the visible spectrum from longest to shortest wavelength?

Answer 13

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

This sequence can be remembered using the acronym ROYGBIV. Each color corresponds to a specific range of wavelengths within the visible spectrum.

Question 14

Which color has the shortest wavelength in the visible spectrum?

Answer 14

Violet

Violet light has the shortest wavelength in the visible spectrum, typically around 380–450 nm.

Question 15

Which color has the longest wavelength in the visible spectrum?

Answer 15

Red

Red light has wavelengths around 620-750 nm.

Question 16

What are ultraviolet rays?

Answer 16

Waves with wavelengths shorter than visible light but longer than X-rays.

UV rays can cause sunburn and are blocked by sunscreen.

Question 17

True or False:

Infrared radiation has a higher frequency than visible light.

Answer 17

False

Infrared has lower frequencies and longer wavelengths than visible light.

Question 18

Fill in the blank:

________ waves have the longest wavelengths in the electromagnetic spectrum.

Answer 18

Radio

Radio waves can have wavelengths ranging from millimeters to kilometers.

Question 19

What is the relationship between wavelength and frequency?

Answer 19

They are inversely proportional.

As wavelength increases, frequency decreases, and vice versa, according to the equation c = λf, where c is the speed of light, λ is the wavelength, and f is the frequency.

Question 20

How does light interact with matter?

Answer 20

It can be reflected, absorbed, or transmitted.

These interactions depend on the material and the light’s wavelength.

Question 21

True or False:

Light travels faster in glass than in air.

Answer 21

False

Light slows down in denser mediums like glass due to interactions with the material.

Question 22

Fill in the blanks:

Transverse waves move ________ to the wave direction, while longitudinal waves move _______ to it.

Answer 22

perpendicular, parallel

This difference affects the types of waves, such as light being transverse and sound being longitudinal.

Question 23

What are mechanical waves?

Answer 23

Waves that require a medium to travel through.

These waves cannot travel through a vacuum because they rely on the vibration of particles in a medium.

Question 24

What are electromagnetic waves?

Answer 24

Waves that do not require a medium and can travel through a vacuum.

These waves consist of oscillating electric and magnetic fields and include visible light, microwaves, and X-rays.

Question 25

# True or False: Mechanical waves **can** travel through a vacuum.

Answer 25

False ## Footnote Mechanical waves require a medium, like air, water, or solid substances, to propagate.

Question 26

What is **amplitude** in a wave?

Answer 26

The **maximum** distance of particles from their equilibrium position. ## Footnote It determines the wave's energy; higher amplitude waves carry more energy.

Question 27

How does amplitude **affect** wave energy?

Answer 27

Higher amplitude waves carry **more** energy. ## Footnote The energy of a wave is directly proportional to the square of its amplitude.

Question 28

# Fill in the blank: **Frequency** in a wave is the number of complete cycles or \_\_\_\_\_\_\_\_\_\_ a wave makes per unit of time.

Answer 28

oscillations ## Footnote Frequency is typically measured in *hertz* (Hz), where 1 Hz equals one cycle per second.

Question 29

What is the **period** of a wave?

Answer 29

The **time** it takes for one complete cycle or oscillation. ## Footnote Period is the inverse of frequency—high frequency waves have shorter periods.

Question 30

How are frequency and period **related**?

Answer 30

Period is the **inverse** of frequency. ## Footnote Period and frequency are inversely related: the period (T) is the time it takes for one complete cycle, calculated as T = 1/f, where f is the frequency.

Question 31

What is **wave speed**?

Answer 31

The **rate** at which a wave propagates through a medium. ## Footnote Wave speed *depends* on both the frequency and wavelength of the wave, and it can be calculated using the formula: Speed = Frequency × Wavelength.

Question 32

# True or False: The wave speed is **constant** for all waves.

Answer 32

False ## Footnote Wave speed **varies** depending on the medium through which the wave is traveling (e.g., sound travels faster in water than in air).

Question 33

# Fill in the blank: If the **frequency** of a wave increases, the \_\_\_\_\_\_\_\_\_\_ decreases.

Answer 33

wavelength ## Footnote This is due to the inverse relationship between frequency and wavelength.

Question 34

What **happens** to the energy of a wave if its frequency increases?

Answer 34

It increases. ## Footnote Energy is directly proportional to frequency, so higher frequency waves have more energy.

Question 35

# True or False: A wave with higher frequency has **lower** energy.

Answer 35

False ## Footnote Higher frequency waves, like gamma rays, carry **more** energy compared to lower frequency waves like radio waves.

Question 36

What is the **formula** for calculating wave speed?

Answer 36

𝑣 = 𝑓𝜆 ## Footnote Where v is wave speed, f is frequency, and λ (lambda) is wavelength.

Question 37

If a wave travels at 50 m/s and has a wavelength of 5 meters, what is its **frequency**?

Answer 37

10 Hz ## Footnote The *frequency* is found by rearranging the formula to 𝑓 = 𝑣 / 𝜆, dividing wave speed by wavelength.

Question 38

A sound wave travels at 340 m/s. If its frequency is 680 Hz, what is its **wavelength**?

Answer 38

0.5 meters ## Footnote To find the wavelength, use the formula 𝜆 = 𝑣 / 𝑓, dividing the wave speed by the frequency.

Question 39

What is the wavelength **range** for visible light?

Answer 39

400 nm and 700 nm. ## Footnote This range is the only part of the electromagnetic spectrum *visible* to the human eye.

Question 40

# Fill in the blank: Light wave is an **example** of a/an \_\_\_\_\_\_\_\_\_\_\_ wave.

Answer 40

electromagnetic ## Footnote Electromagnetic waves, such as light, do not require a medium and can travel through space.

Question 41

# True or False: Amplitude **affects** the speed of the wave.

Answer 41

False ## Footnote The speed of a wave is determined by the properties of the medium, not its amplitude.

Question 42

What is **reflection**?

Answer 42

The way that **light bounces** when it hits a surface. ## Footnote It occurs when light interacts with a boundary and does not pass through it, such as when a *mirror* reflects light.

Question 43

What is **refraction**?

Answer 43

The **bending of light** as it passes from one medium to another. ## Footnote Refraction occurs due to a change in the speed of light.

Question 44

What is **polarization** of light?

Answer 44

The **alignment of light waves** in a specific direction. ## Footnote For example, polarized sunglasses use this principle to block horizontally polarized light, which significantly reduces glare from reflective surfaces like water, glass, or roads, enhancing visibility and comfort.

Question 45

What causes a **rainbow**?

Answer 45

Refraction, dispersion, and reflection of **light** in water droplets. ## Footnote Different wavelengths are refracted by different amounts, separating the colors.

Question 46

# Fill in the blank: \_\_\_\_\_\_\_\_ is the **splitting** of white light into its constituent colors when passing through a prism.

Answer 46

Dispersion ## Footnote Dispersion occurs because *different* wavelengths of light refract by different amounts.

Question 47

# True or False: Violet refracts the **most** during dispersion.

Answer 47

True ## Footnote Violet light has the *shortest* wavelength and *highest* refractive index, causing it to bend more than other colors.

Question 48

What is **total internal reflection**?

Answer 48

**Complete** reflection of light within a medium above the critical angle. ## Footnote This phenomenon happens only when light travels from a denser to a less dense medium, like glass to air.

Question 49

What are **optical fibers** an example of?

Answer 49

Total internal reflection ## Footnote Optical fibers use total internal reflection to transmit light signals over long distances without significant loss.

Question 50

# True or False: Total internal reflection **occurs** when the angle of incidence is less than the critical angle.

Answer 50

False ## Footnote Total internal reflection only occurs when the angle of incidence exceeds the critical angle.

Question 51

# Define: Diffraction

Answer 51

The **bending of light waves** around obstacles or through small openings. ## Footnote This phenomenon explains effects like the spreading of sound around corners or the patterns observed in light passing through narrow slits.

Question 52

What is **interference**?

Answer 52

The **interaction** of two or more waves that results in a new wave pattern. ## Footnote Interference can be *constructive* (amplifying) or *destructive* (canceling).

Question 53

What is the **principle** of superposition?

Answer 53

When waves overlap, the resulting wave is the **sum** of their displacements. ## Footnote This principle explains phenomena like standing waves and interference patterns.

Question 54

# True or False: Destructive interference **occurs** when the crest of one wave overlaps with the crest of another.

Answer 54

False ## Footnote Destructive interference occurs when a crest overlaps with a trough, canceling the wave out.

Question 55

# Fill in the blank: Light waves vibrating in **all** directions are converted into a single plane through \_\_\_\_\_\_\_\_.

Answer 55

polarization ## Footnote Polarized light is often used to reduce glare.

Question 56

What **type** of waves can be polarized?

Answer 56

Transverse waves. ## Footnote Only *transverse waves*, like light, can be polarized because their oscillations are perpendicular to wave direction.

Question 57

# Fill in the blank: The **process** by which a material takes in light energy and converts it into heat is called \_\_\_\_\_\_\_\_.

Answer 57

absorption ## Footnote Dark-colored objects absorb more light, converting it into heat energy.

Question 58

What is **scattering**?

Answer 58

The **redirection** of light by particles in its path. ## Footnote Rayleigh scattering *explains* why the sky appears blue, as shorter wavelengths scatter more.

Question 59

What is the **term** for light passing through a material?

Answer 59

Transmission ## Footnote Transparent materials like glass allow light to pass through with minimal scattering.

Question 60

# True or False: Scattering **only** occurs in the atmosphere.

Answer 60

False ## Footnote Scattering can occur in any medium containing particles that interact with light.

Question 61

What **causes** the red color of sunsets?

Answer 61

Scattering of **shorter** wavelengths, leaving longer ones like red. ## Footnote At sunset, sunlight passes through more atmosphere, scattering blue light away.

Question 62

What is the **Doppler effect**?

Answer 62

The **change in frequency or wavelength due to motion** of the observer or source. ## Footnote This effect is *noticeable* with sound, like a siren changing pitch as it passes.

Question 63

What **happens** to the pitch of a sound as the source approaches an observer?

Answer 63

It increases. ## Footnote According to the Doppler effect, this occurs because the sound waves are compressed, increasing their frequency.

Question 64

What are three main types of of **mirrors**?

Answer 64

1. Plane 2. Convex 3. Concave ## Footnote Light interacts differently with each type of mirror.

Question 65

What is a **plane mirror**?

Answer 65

A mirror with a **flat** surface. ## Footnote These mirrors reflect light to form an image that is the same size as the object but reversed.

Question 66

What is the **focal point** of a plane mirror?

Answer 66

It **doesn't** have a focal point. ## Footnote They reflect light without converging or diverging it, so they don’t have a real focal point.

Question 67

What is a **convex mirror**?

Answer 67

A mirror with a curved surface that bulges **outward**. ## Footnote These mirrors diverge light rays, which results in smaller, virtual, and upright images.

Question 68

What is a **concave mirror**?

Answer 68

A mirror with a curved surface that curves **inward** like a bowl. ## Footnote These mirrors can converge light rays, forming real or virtual images depending on the object’s position relative to the focal point.

Question 69

# True or False: Convex mirrors **always** form virtual images.

Answer 69

True ## Footnote Convex mirrors always form virtual, diminished images regardless of the object's position.

Question 70

# Fill in the blank: The **focal point** of a concave mirror is where the \_\_\_\_\_\_\_ rays converge.

Answer 70

parallel ## Footnote The focal point is the point where parallel rays of light meet after being reflected by the concave mirror.

Question 71

In which **applications** are concave mirrors generally used?

Answer 71

Shaving mirrors and telescopes. ## Footnote Concave mirrors are used to magnify images, such as in shaving mirrors or optical telescopes for better focus on distant objects.

Question 72

What is a **lens**?

Answer 72

A **transparent** object that refracts light to form an image. ## Footnote Lenses can converge or diverge light depending on their *shape* (convex or concave).

Question 73

What type of **image** is formed by a convex lens when the object is beyond the focal point?

Answer 73

Real and inverted. ## Footnote When the object is placed beyond the focal point, a convex lens forms a real and inverted image on the opposite side of the lens.

Question 74

What is a **concave** lens?

Answer 74

A lens that is **thinner** in the middle than at the edges. ## Footnote Concave lenses diverge light rays, forming a virtual, upright, and diminished image.

Question 75

# True or False: Convex lenses **always** form real images.

Answer 75

False ## Footnote Convex lenses can form both real and virtual images depending on the position of the object relative to the focal point.

Question 76

# Fill in the blank: \_\_\_\_\_\_ lenses are used in **microscopes**.

Answer 76

Convex ## Footnote These lenses magnify small objects by converging light and forming a magnified image.

Question 77

What **happens** to light as it passes through a lens?

Answer 77

It **refracts**, bending toward or away from the optical axis. ## Footnote The degree of refraction depends on the curvature and material of the lens, which affects the image formed.

Question 78

What **type** of wave is sound?

Answer 78

Longitudinal (compression) wave. ## Footnote In this kind of wave, particles move back and forth in the same direction as the wave, creating compressions and rarefactions.

Question 79

What is a **compression** in a sound wave?

Answer 79

A **region** where particles are closest together. ## Footnote It occurs when the particles of the medium are compressed, creating areas of *high pressure* in the sound wave.

Question 80

# True or False: Sound waves **can** travel through a vacuum.

Answer 80

False ## Footnote Sound **requires** a medium (such as air, water, or solid materials) to travel. It cannot travel through a vacuum because there are no particles to vibrate.

Question 81

What is the **speed** of sound in air?

Answer 81

Approximately **343 m/s** at room temperature. ## Footnote The speed of sound depends on the medium (e.g., air, water, or solid materials) and temperature. It is faster in warmer air and in denser media.

Question 82

What **determines** the pitch of a sound?

Answer 82

The **frequency** of the sound wave. ## Footnote High-frequency sound waves produce high-pitched sounds, while low-frequency waves produce low-pitched sounds.

Question 83

# True or False: The loudness of sound is directly **related** to its frequency.

Answer 83

False ## Footnote Loudness is related to the **amplitude** of the sound wave, not its frequency. High amplitude means louder sound, regardless of pitch.

Question 84

How is sound intensity **measured**?

Answer 84

In **decibels** (dB). ## Footnote *Decibels* are a logarithmic unit used to measure sound intensity. A 10 dB increase represents a tenfold increase in intensity.

Question 85

What does the human ear perceive as **louder** sound?

Answer 85

A sound with **greater** amplitude. ## Footnote As the amplitude of a sound wave increases, the energy transferred through the medium increases, making the sound appear louder to the human ear.

Question 86

# Fill in the blank: A sound with a **low** frequency is perceived as a \_\_\_\_\_\_ pitch.

Answer 86

low ## Footnote Low-frequency sound waves produce lower-pitched sounds, such as those from a bass drum or thunder.

Question 87

What is the **threshold** of hearing?

Answer 87

The **quietest** sound detectable, typically at 0 dB. ## Footnote It *corresponds* to the lowest sound intensity that can be perceived, below which sound is inaudible.

Question 88

What **happens** to the pitch of a sound as its frequency increases?

Answer 88

It becomes **higher**. ## Footnote As the frequency of sound increases, the number of vibrations per second increases, leading to a higher-pitched sound.

Question 89

# True or False: The Doppler effect **only** applies to sound waves.

Answer 89

False ## Footnote The Doppler effect applies to **all** types of waves, including light waves in astronomy.

Question 90

What **happens** to the frequency of a sound as the source moves away from the observer?

Answer 90

It decreases. ## Footnote As the sound source moves away, the waves are stretched, decreasing the frequency and lowering the pitch.