6 - Light, Sound and Energy

Question 1

Define:

wave

Answer 1

A motion that carries energy from one place to another.

Waves can be mechanical (requiring a medium) or electromagnetic (traveling through space without a medium).

Question 2

Explain:

What are the basic properties of a wave?

Answer 2

• Wavelength
• Frequency
• Amplitude
• Speed

These properties help determine the wave’s energy, behavior, and type of application.

Wavelength: The distance between two consecutive crests or troughs.

Frequency: The number of wave cycles that pass a point in one second.

Amplitude: The height of the wave, indicating its energy.

Speed: How fast the wave travels through a medium.

Question 3

Identify:

What is the unit of frequency?

Answer 3

hertz

(Hz)

Frequency, measured in hertz (Hz), is the number of wave cycles that pass a point in one second and is inversely related to wavelength for waves traveling at the same speed.

Question 4

Identify:

What formula relates wave speed, frequency, and wavelength?

Answer 4

𝑣=𝑓λ

where:

𝑣: Wave speed
𝑓: Frequency
𝜆: Wavelength

Question 5

Explain:

A wave has a frequency of 500 Hz and a wavelength of 2 m. What is its speed?

Answer 5

1000 m/s

Solution:
Use the formula:
v = f × λ
v = 500 Hz × 2 m = 1000 m/s

Question 6

True or False:

The wave speed formula changes depending on the type of wave.

Answer 6

False

While the values for v, f, and λ vary, the formula remains consistent across wave types.

Question 7

Identify:

What is the bending of a wave between mediums called?

Answer 7

refraction

Refraction explains the bending of light in water, creating visual distortions like the bent straw effect.

Question 8

Explain:

Why does refraction occur?

Answer 8

Because waves change speed in mediums of different densities.

The bending angle depends on the refractive index of the materials involved and the wave’s speed in each medium.

Question 9

Identify:

What is the process of a wave bouncing back after hitting a barrier?

Answer 9

reflection

Reflection follows the law of reflection: the angle of incidence equals the angle of reflection.

Question 10

Define

diffraction

Answer 10

Occurs when waves bend around obstacles.

Diffraction is observed when waves pass through narrow openings or around barriers.

Question 11

Describe:

How does wave interference occur?

Answer 11

When two or more waves overlap, they combine to form a new wave pattern.

Constructive interference amplifies wave amplitude, while destructive interference reduces it, impacting wave energy.

Question 12

Define:

amplitude

Answer 12

Measure of the size or intensity of a wave.

Amplitude represents the wave’s height; higher amplitude means more energy, influencing sound loudness and light brightness.

Example: In sound waves the amplitude of a sound wave corresponds to its loudness. A sound wave with a larger amplitude will be louder than a sound wave with a smaller amplitude.

Question 13

Identify:

What is the time it takes for one complete cycle of the wave to pass a given point?

Answer 13

period

Period and frequency are inversely related: T = 1/f, where T is the period and f is the frequency.

Question 14

Explain:

What are the factors that affect wave speed?

Answer 14

• Type of Wave
• Medium
• Temperature and Density

Type of Wave: Mechanical waves need a medium; electromagnetic waves do not.

Medium: Wave speed varies with the material (air, water, or solid).

Temperature and Density: Higher temperatures and lower densities increase speed in mechanical waves.

Question 15

Define:

Doppler effect

Answer 15

A shift in wave frequency caused by motion.

The Doppler effect occurs when the source of a wave and an observer are in relative motion, causing changes in frequency. This explains the change in pitch of a passing siren and redshift observed in astronomy.

Question 16

Identify::

What type of wave requires a medium to travel through?

Answer 16

mechanical waves

Mechanical waves transfer energy through particle vibrations, as in air or water.

Question 17

Identify:

What type of waves are responsible for the transmission of energy through Earth’s crust?

Answer 17

seismic

Seismic waves are essential for monitoring earthquakes and understanding geological processes.

Question 18

Identify:

Do sound waves travel faster in gases or solids?

Answer 18

solids

The density and elasticity of solids allow sound waves to travel faster compared to gases.

Question 19

Explain:

How does temperature affect the speed of sound?

Answer 19

Higher temperatures speed up sound as particles transfer energy faster.

In air, sound speed increases by approximately 0.6 m/s for every 1°C increase in temperature.

Question 20

Define:

longitudinal wave

Answer 20

A wave where particles move parallel to the wave’s direction of travel.

Longitudinal waves transfer energy through compressions and rarefactions. Common examples include sound waves in air and compression waves in springs.

Question 21

Identify:

What type of wave is light?

Answer 21

electromagnetic

Light is part of the electromagnetic spectrum and does not require a medium to travel.

Question 22

Identify:

What part of the electromagnetic spectrum is visible to the human eye?

Answer 22

Visible light

Visible light ranges from 400 nm (violet) to 700 nm (red) in wavelength, bridging infrared and ultraviolet radiation.

Question 23

Explain:

List the parts of the electromagnetic spectrum in increasing frequency.

Answer 23

• Radio Waves
• Microwaves
• Infrared Waves
• Visible Light
• Ultraviolet Waves
• X-rays
• Gamma Rays

Radio Waves: Longest wavelength, used for communication like radio and TV signals.

Microwaves: Shorter wavelength than radio waves, used in cooking and radar technology.

Infrared Waves: Detected as heat, used in thermal imaging and remote controls.

Visible Light: The only part of the spectrum visible to the human eye, seen as colors.

Ultraviolet Waves: Higher energy, causes sunburn and is used in sterilization.

X-rays: High energy, used in medical imaging to view inside the body.

Gamma Rays: Highest frequency and energy, used in cancer treatment and produced by nuclear reactions.

Question 24

Explain:

Why are gamma rays dangerous?

Answer 24

They have high energy and can penetrate tissues, causing cellular damage.

Gamma rays are used in cancer therapy due to their ability to target and destroy harmful cells.

Question 25

# Explain: How is **infrared radiation** different from **ultraviolet radiation**?

Answer 25

Infrared has **longer wavelengths** and **less energy** than ultraviolet. ## Footnote *Infrared* is associated with heat, while ultraviolet can cause skin damage and sterilize surfaces.

Question 26

# True or False: **X-rays** are part of the **electromagnetic spectrum**.

Answer 26

True ## Footnote **X-rays** are widely used for imaging internal body structures due to their high penetration ability.

Question 27

# Define: What is **energy transfer**?

Answer 27

The **movement of energy** from one object or system to another. ## Footnote Energy transfer allows energy to move between systems, powering countless natural and technological processes.

Question 28

# Explain: What are the **3 primary methods** of energy transfer?

Answer 28

1. Conduction 1. Convection 1. Radiation ## Footnote **Conduction**: Energy transfer through direct contact, typically in solids. **Convection**: Energy transfer through fluid movement in liquids or gases. **Radiation**: Energy transfer through electromagnetic waves, even in empty space.

Question 29

# Identify: What is the method of **energy transfer** through **direct contact** of particles?

Answer 29

conduction ## Footnote In **conduction**, thermal energy flows from regions of higher to lower temperature through a solid medium.

Question 30

# Define: convection

Answer 30

Way that heat moves through liquids and gases. ## Footnote Example: **Boiling water** - When you boil water in a pot, the heat from the bottom makes the water at the bottom warmer and less dense. This warm water rises, while the cooler water at the top sinks, creating a convection current that heats the entire pot of water.

Question 31

# Explain: What metals are **good conductors** of heat?

Answer 31

* Copper * Aluminum * Silver * Gold * Iron ## Footnote **Copper**: Used in cookware and wiring **Aluminum**: Found in heat sinks and foil **Silver**: Best conductor but costly **Gold**: Corrosion-resistant for electronics **Iron**: Durable, used in pans and tools These metals are efficient conductors due to their ability to quickly transfer thermal energy via free electrons.

Question 32

# Explain: Why are metals **good conductors** of heat?

Answer 32

Because their **free electrons** transfer energy **efficiently**. ## Footnote The mobility of electrons in metals enables *rapid energy distribution* across the material.

Question 33

# Identify: What are materials that **resist** the flow of thermal energy?

Answer 33

insulators ## Footnote **Examples**: rubber, wood, and plastic

Question 34

# Explain: How does **radiation** differ from **conduction** and **convection**?

Answer 34

Radiation **transfers energy** without requiring particles or a medium. ## Footnote Unlike *conduction* and *convection*, which rely on particles for energy transfer, *radiation* can travel through a vacuum. This is why heat from the Sun can reach Earth through the emptiness of space.

Question 35

# Identify: What is an **example** of radiation in **everyday life**?

Answer 35

Sunlight warming your skin. ## Footnote Radiation from the Sun includes v*isible light*, *infrared*, and *ultraviolet rays*.

Question 36

# Define: thermal equilibrium

Answer 36

A **state** where **no net energy transfer occurs** between objects in contact. ## Footnote Objects at the same temperature are in thermal equilibrium, stopping *heat flow*.

Question 37

# Define: latent heat

Answer 37

Energy during a phase change **without** changing temperature. ## Footnote Latent heat is *crucial* for processes like melting, freezing, evaporation, and condensation, enabling phase transitions.

Question 38

# Explain: What are the **two types** of **latent heat**?

Answer 38

1. Latent Heat of Fusion 1. Latent Heat of Vaporization ## Footnote **Latent Heat of Fusion**: Energy required to change a substance between solid and liquid without temperature change. **Latent Heat of Vaporization**: Energy required to change a substance between liquid and gas without temperature change.

Question 39

# Explain: What are the **phase transitions** involved in the **water cycle**?

Answer 39

* Evaporation * Condensation * Freezing * Melting * Sublimation * Deposition ## Footnote **Evaporation**: Liquid water absorbs energy and becomes vapor. **Condensation**: Water vapor cools and forms liquid droplets. **Freezing**: Liquid water loses energy and turns into ice. **Melting**: Ice absorbs energy and becomes liquid water. **Sublimation**: Ice directly turns into vapor without becoming liquid. **Deposition**: Water vapor turns directly into ice without becoming liquid.

Question 40

# True or False: **Latent heat** causes **temperature changes** during phase transitions.

Answer 40

False ## Footnote During phase transitions, energy is used to *break* or *form* bonds, not to increase temperature.

Question 41

# Explain: Why is **latent heat** important in the **water cycle**?

Answer 41

It drives phase changes like **evaporation** and **condensation**. ## Footnote These processes *distribute* heat across the atmosphere and regulate Earth's climate.

Question 42

# Describe: What is the role of **latent heat** during **evaporation**?

Answer 42

Energy is **absorbed** to turn liquid water into vapor. ## Footnote This energy transfer cools the surface and releases stored heat during condensation.

Question 43

# True or False: Melting ice **absorbs energy** from its **surroundings**.

Answer 43

True ## Footnote The latent heat of fusion is absorbed to **break** molecular bonds in the ice, transitioning it to liquid.

Question 44

# Define: Earth’s energy budget

Answer 44

The **balance** between incoming solar energy and outgoing energy from Earth. ## Footnote *Phase transitions*, particularly latent heat, play a critical role in maintaining this balance.

Question 45

# Explain: How does **evaporation** impact **Earth’s energy budget**?

Answer 45

It **absorbs heat** as **latent energy**. ## Footnote Evaporation absorbs heat, storing it as latent energy in water vapor. This energy is *released back* into the atmosphere during *condensation*, helping distribute heat globally.

Question 46

# Define: deposition

Answer 46

Process where a gas changes directly into a solid without going through the liquid phase. ## Footnote **Example**: Frost forming on a cold surface. Water vapor in the air changes directly into ice crystals.  

Question 47

# True or False: Sublimation **absorbs energy** from the **environment**.

Answer 47

True ## Footnote **Sublimation** is the transition from solid to gas, requiring latent heat to overcome molecular bonds.