Energy Transformation, Heat Transfer, and Wave Phenomena of Sound and Light

Energy cannot be created or destroyed; it only transforms into different forms.
Transferring energy refers to movement from one place to another, while transforming refers to changing types.

Particles at a warm end gain kinetic energy and vibrate more, transferring energy to neighbouring particles.
Heat flow continues until the temperature is uniform and energy is shared evenly.
Metals are the best conductors because their electrons are free to move and transfer kinetic energy.
Insulators are poor conductors, such as air, foam, and wool.
Thermal conductivity explains why materials at the same temperature feel different; for example, tile feels colder than carpet because it conducts heat away from the skin faster.
Heat vs. Temperature: Two saucepans at $100\,^{\circ}C$ have the same temperature, but the one with more particles (Saucepan A) has more overall heat energy than the one with fewer particles (Saucepan B).

Occurs when heated particles gain kinetic energy, spread out, and become less dense.
Less dense heated air/liquid rises, while cooler, denser air/liquid sinks to replace it.
This cycle of heating, rising, cooling, and falling is called a convection current.

Heat is transferred via electromagnetic radiation or light without the need for particles (e.g., heat from the Sun reaching Earth).
Radiant heat interacts with matter in three ways:
- Reflected: Shiny or light-colored surfaces reflect heat; temperatures do not change quickly.
- Transmitted: Clear objects like glass allow radiant heat to pass through; temperatures do not increase quickly.
- Absorbed: Dark-colored objects absorb radiant heat; temperatures increase quickly.

How does wearing several layers of clothing keep a person warm? Layers trap air, which is a poor conductor (insulator), preventing body heat from escaping.
How does heat move along a metal frying pan handle? Heat moves via conduction. Particles near the heat source vibrate more and collide with neighboring metal particles, transferring kinetic energy along the handle to the hand.
Why wrap a cloth around a hot metal handle? The cloth acts as an insulator (poor conductor) to slow the transfer of heat to the hand and prevent burns.

Energy is transmitted via waves through vibrations without the particles themselves traveling across the distance.
Transverse waves: Vibrations are up and down or perpendicular to the direction of travel (e.g., ripples in a pond, light, vibrations on a string).
Longitudinal waves: Vibrations move forwards and backwards; also known as compression waves (e.g., sound waves, shock waves).
Key Properties:
- Wavelength
- Frequency
- Amplitude

Sound is a mechanical longitudinal wave that requires particles to travel; it cannot travel through a vacuum.
The speed of sound increases in denser materials (faster in solids and liquids than gases) and warmer materials.
Speed of sound in air is approximately $330\,m/s$ at $0\,^{\circ}C$ and $350\,m/s$ at $25\,^{\circ}C$ .
Echo: A reflected sound wave. Total distance traveled is twice the one-way distance to the object.
Ear Anatomy:
- Outer Ear: Auricle, Ear canal.
- Middle Ear: Eardrum, Hammer, Anvil, Stirrup, Oval window, Eustachian tube.
- Inner Ear: Semicircular canals, Cochlea, Auditory nerve.
Loudness: Measured in decibels ( $dB$ ). Higher $dB$ means more energy. Examples include Breathing ( $10\,dB$ ), Conversation ( $60\,dB$ ), and Jet engines ( $140\,dB$ ). The threshold of pain is around $130\,dB$ - $140\,dB$ .
Hearing Loss: Temporary loss can be caused by wax or noise; permanent loss results from damage to the middle or inner ear. Hearing aids amplify sound or transmit vibrations through bone.

Electromagnetic waves are transverse waves that can travel through a vacuum at approximately $300,000,000\,m/s$ .
Spectrum order (increasing frequency): Radio waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma rays.
Light interacts with matter as follows:
- Transparent: Lets light through clearly.
- Translucent: Scatters some light.
- Opaque: Does not allow light through.

Law of Reflection: Light is reflected at the same angle that it is incident ( $\text{Angle of Incidence} = \text{Angle of Reflection}$ ).
Mirrors:
- Plane: Same size, distance, and upright, but laterally reversed.
- Convex: Smaller, upright, wide-angle images (used in security).
- Concave: Can be magnified or upside-down (used in makeup mirrors).
Refraction: The bending of light as it changes speed entering a new medium.
- FAST Acronym: Faster Away (from normal), Slower Toward (the normal).
- Light bends toward the normal when entering a denser medium (like glass).
Lenses:
- Convex (Biconvex): Converges parallel rays to a real focal point.
- Concave (Biconcave): Diverges light rays; they appear to come from a virtual focal point.