5A2 Wave Phenomena

Question 1

Define:

Wave reflection

Answer 1

The change in direction of propagation of a wave that strikes a boundary between two materials.

Wave reflection occurs when a wave meets a barrier and bounces off in another direction.

Question 2

Define:

Angle of incidence

Answer 2

The angle between the incident ray and the normal line at the point of contact.

The normal is a perpendicular line to the surface at the point where the wave strikes the surface.

Question 3

What does the law of reflection state?

Answer 3

The angle of incidence is equal to the angle of reflection.

Mathematically, it can be written as θi = θr, where θi is the angle of incidence and θr is the angle of reflection.

Question 4

Fill in the blank:

_____ ______ is the bending of waves as it passes from one medium to another.

Answer 4

Wave refraction

It occurs when a wave hits the surface of a different medium.

Question 5

What happens to a light ray when it passes from air to water?

Answer 5

The light ray slows down and bends toward the normal line.

The normal is the line perpendicular to the air-water interface.

Question 6

What is the index of refraction?

Answer 6

It quantifies the ratio between the speed of light in a vacuum and the speed of light in the material.

It is expressed as n = c/v and is dimensionless.

Question 7

True or false:

Snell’s Law relate the incident angle and the refracted angle.

Answer 7

True

It is based on the indices of refraction of both materials.

Question 8

What is the equation for Snell’s Law?

Answer 8

n1sin(θ1) = n2sin(θ2)

Here, n1 and n2 are the indices of refraction for the two materials, and θ1 and θ2 are the incident and refracted angles, respectively.

Question 9

What happens to light when it passes from a material with a higher index of refraction to a lower index?

Answer 9

Light bends away from the normal line.

If the incident angle is large enough, total internal reflection occurs.

Question 10

When does total internal reflection occur?

Answer 10

It occurs when all light is reflected back into a material instead of passing into another material.

This phenomenon is utilized in fiber optic cables.

Question 11

True or false:

The critical angle is the angle of incidence at which total internal reflection occurs.

Answer 11

True

It can be calculated using the indices of refraction of the two materials.

Question 12

Define:

Diffraction

Answer 12

Bending of light waves around obstacles or the spreading of light waves as they pass through small openings.

The extent of diffraction depends on the size of the obstacle or slit compared to the wavelength of the light.

Question 13

True or false:

Diffraction only occurs when light passes through very large openings.

Answer 13

False

Diffraction occurs when light passes through openings or around obstacles that are comparable in size to the wavelength of the light. Diffraction is most noticeable when the size of the slit or obstacle is on the order of the wavelength of the light.

Question 14

True or false:

Interference patterns can only occur with light waves.

Answer 14

False

All waves—sound, water, or light—can show interference through superposition.

Question 15

What is the condition for destructive interference?

Answer 15

When waves are out of phase with a path difference of (2n+1)λ/2,

It reduces wave amplitude, forming dark fringes in patterns.

Question 16

How does the uncertainty principle affect the double-slit experiment?

Answer 16

It limits observing both particle and wave behavior at the same time.
## Footnote

The principle indicates that measuring one property disturbs the other.

Question 17

Fill in the blank:

The double-slit experiment shows that light can behave like a _____.

Answer 17

wave

This behavior is evidenced by the interference patterns observed in the experiment.

Question 18

True or false:

In Young’s double-slit experiment, the bright fringes occur at angles where the path difference is an integer multiple of the wavelength.

Answer 18

True

Bright fringes are produced when there is constructive interference.

The condition for constructive interference is d * sin(θ) = m * λ, where d is the slit separation, θ is the angle of the bright fringe, m is an integer (order of the fringe), and λ is the wavelength of light.

Question 19

What kind of light source is used in Young’s double-slit experiment?

Answer 19

A monochromatic source of light.

This ensures a single wavelength is used for the experiment.

Question 20

Define:

polarization

in the context of light

Answer 20

Filtering out chaotic light-wave oscillations to achieve a clearer experience of light.

Polarization allows light to oscillate in a specific direction, making it more organized.

Question 21

How does polarized light differ from unpolarized light?

Answer 21

Polarized light vibrates in one direction; unpolarized light vibrates in many.

Sunlight is unpolarized; polarizing filters produce polarized light.

Question 22

What is a polarizer?

Answer 22

A device that allows light oscillating in a particular direction to pass through while blocking other directions.

Think of it like a card with slits that only permits certain light waves.

Question 23

List some uses of polarizers.

Answer 23

• Polarizing sunglasses
• Polarizing filters for cameras
• LCD screens
• Radio transmissions

These applications utilize the ability of polarizers to manage light in various contexts.

Question 24

What does Malus’s Law describe?

Answer 24

The relationship between the intensity of light that passes through a polarizer and the angle of oscillation.

It quantifies how much light is lost when passing through a polarizer.

Question 25

# Fill in the blank: **Malus's Law** indicates that the intensity of light that passes through a **polarizer** is equal to the original intensity multiplied by \_\_\_\_\_\_.

Answer 25

cos²(θ) ## Footnote The squared term is crucial in the calculation.

Question 26

# True or false: The **reflected light** becomes **polarized**.

Answer 26

True ## Footnote This polarization can be managed by polarizers to reduce glare.

Question 27

# True or false: **Brewster's Law** allows us to find the angle at which the reflected light becomes completely polarized.

Answer 27

True ## Footnote At Brewster's angle, the reflected light is completely polarized, and this principle is used in various optical applications.

Question 28

What is the **formula** for Brewster's angle?

Answer 28

θB = tan⁻¹(n2/n1) ## Footnote θB is Brewster's angle, and n1 and n2 are the refractive indices of the two media.

Question 29

How do **polarizing filters** work in **photography**?

Answer 29

They allow only certain polarized light rays to pass through, reducing reflections and enhancing contrast. ## Footnote They are particularly effective for darkening skies and eliminating reflections from glass or water.

Question 30

# Define: Scattering of light

Answer 30

The **diffusive effect of particles** causing light waves to deviate from their straight paths. ## Footnote It involves absorption and re-emission of light in various **directions**.

Question 31

What are the two **main types** of scattering of light?

Answer 31

* Elastic scattering * Inelastic scattering ## Footnote Elastic scattering has no change in wavelength, while inelastic scattering involves a change in the inner energy of molecules.

Question 32

What is an example of **inelastic scattering**?

Answer 32

Raman scattering ## Footnote It involves the interaction of light with molecules resulting in a **loss or gain of energy**.

Question 33

What is **Rayleigh** scattering?

Answer 33

It occurs when **light interacts with particles that are much smaller** than the wavelength of the light in question. ## Footnote This causes shorter wavelengths to scatter more than longer wavelengths.

Question 34

# True or false: **Mie scattering** explain blue color of the sky.

Answer 34

False ## Footnote This phonomenon is explained by Rayleigh scattering.

Question 35

What is the **Tyndall effect**?

Answer 35

The **scattering of light by particles in a colloid or fine suspension**, making the light beam visible. ## Footnote This effect is often seen when sunlight passes through fog or dusty air.

Question 36

# Fill in the blank: \_\_\_\_\_\_ ___________ occurs when the scattering particles are **comparable to or larger than the wavelength of the incident light**, resulting in less wavelength-dependent scattering.

Answer 36

Mie scattering ## Footnote It explains the white appearance of clouds, as it affects all visible wavelengths equally.

Question 37

What happens to light during a **reddish sunset**?

Answer 37

**Longer wavelengths reach the eyes** as shorter wavelengths are scattered away. ## Footnote The sun's rays travel a longer distance through the atmosphere at sunset.

Question 38

What is wave **absorption**?

Answer 38

The **transfer of energy from a wave to a medium**, such as solid, liquid, or gas. ## Footnote Wave absorption occurs when waves like sound or light hit a medium and transfer energy.

Question 39

What happens to the **energy** of a wave during **absorption**?

Answer 39

The energy is **converted into heat** as the atoms and molecules within the object vibrate. ## Footnote Sometimes the wave is only partially absorbed, leading to lower energy levels being transferred.

Question 40

Why do **black objects** appear black?

Answer 40

They absorb all colors of visible light, holding a great amount of energy and transferring it to heat. ## Footnote This is why many homes have black roofs, which help keep them cool by trapping heat.

Question 41

# Fill in the blank: Soft materials **absorb sound waves** to decrease noise levels, changing the \_\_\_\_\_\_\_ and lowering the volume.

Answer 41

frequency ## Footnote Foam padding is an example of a material used for soundproofing.

Question 42

What does **wave dispersion** describe?

Answer 42

The separation of light of different frequencies by different amounts. ## Footnote This is often demonstrated using a prism to separate white light into colors.

Question 43

How do **rainbows** form?

Answer 43

Through **reflection, refraction,** and **dispersion** of light. ## Footnote **Dispersion** separates white light into its components based on varying wavelengths.

Question 44

What is the difference between **dispersion** and **diffusion**?

Answer 44

* Dispersion is **predictable** based on frequency. * Diffusion is **random**. ## Footnote Diffusion occurs when light is scattered off a rough surface or passes through an irregular medium.

Question 45

What happens when light is **transmitted** through a material?

Answer 45

Light passes through the medium without being **absorbed or reflected**, although it may be refracted depending on the material’s properties. ## Footnote The amount of transmission depends on the material’s transparency and the wavelength of the light.

Question 46

# True or false: A **material's transparency** determines how much light can pass through it.

Answer 46

True ## Footnote Transparent materials allow most light to pass through, while opaque materials block it completely.

Question 47

What is the difference between wave **absorption**, wave **transmission**, and wave **reflection**?

Answer 47

Absorption involves energy being taken in, transmission involves passing through without energy transfer, and reflection involves bouncing back. ## Footnote Examples include light waves hitting mirrors (reflection) and light passing through windows (transmission).

Question 48

# Define: Natural frequency

Answer 48

Frequency at which a system **tends to oscillate** when disturbed from its rest position without external forces acting on it. ## Footnote Every object or system has its own characteristic natural frequency.

Question 49

What is **resonance** in a physical system?

Answer 49

It occurs when an object or system vibrates at its **natural frequency** due to an external force, causing an increase in amplitude. ## Footnote This phenomenon can be observed in musical instruments, bridges, or even in the design of buildings.

Question 50

# Fill in the blank: The **frequency of the second harmonic** is ______ the fundamental frequency.

Answer 50

twice ## Footnote Each successive harmonic is an integer multiple of the fundamental frequency.

Question 51

What is the relationship between **resonance and harmonics**?

Answer 51

Resonance happens when an **external force matches a harmonic frequency**, amplifying the vibration. ## Footnote Higher harmonics can also resonate if their frequencies match the driving force’s frequency.

Question 52

# True or false: When the **source** of the wave is moving towards the **observer**, the **frequency** of the wave increases.

Answer 52

True ## Footnote This is explained by the **Doppler effect**. When the source approaches the observer, the waves are compressed, resulting in a higher observed frequency (blue shift for light waves).

Question 53

How does sound change when an **observer moves toward a stationary source**?

Answer 53

The sound's frequency and pitch **appear higher**. ## Footnote More wavefronts reach the observer per second, increasing perceived frequency.

Question 54

# True or false: The **Doppler effect** can be observed with both sound and light waves.

Answer 54

True ## Footnote For light, the effect causes a shift toward the blue end of the spectrum when moving toward the observer (blue shift) and toward the red end when moving away (red shift).

Question 55

What is the **general formula** for the Doppler effect?

Answer 55

f'=f[(v±v0)/(v±vs)] ## Footnote Where f' is the observed frequency, f is the emitted frequency, v is the wave speed, v0 is the observer's speed, and vs is the source’s speed.

Question 56

How is the **Doppler effect** used in **astronomy**?

Answer 56

It helps astronomers determine the **motion of stars** and galaxies by analyzing the red and blue shifts in light from these objects. ## Footnote The red shift indicates objects are moving away, while blue shift indicates they are moving toward Earth.