Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Light energy travels in straight lines as waves. It can be reflected (bouncing off), refracted (bending when passing through different media), or absorbed. The speed of light is denoted by .
Sound energy is produced by vibrations and moves as longitudinal waves. It requires a medium (solid, liquid, or gas) to travel. Pitch is determined by the frequency () of the vibration, while volume is determined by the amplitude ().
Heat energy, or thermal energy, is the flow of energy from an object at a higher temperature () to an object at a lower temperature (). This transfer continues until thermal equilibrium is reached where .
Materials can be classified by how they interact with light: transparent (all light passes), translucent (some light passes), and opaque (no light passes, creating a shadow where light is blocked).
Heat transfer occurs through three main methods: conduction (solids), convection (liquids and gases), and radiation (electromagnetic waves).
📐Formulae
💡Examples
Problem 1:
If a sound wave has a frequency of and a wavelength of , calculate the speed () of the sound wave.
Solution:
Explanation:
By using the wave equation , we multiply the frequency by the wavelength to find that the sound is traveling at through the air.
Problem 2:
A cup of cocoa is at and the surrounding air is . In which direction will the heat energy flow?
Solution:
From the cocoa () to the air ().
Explanation:
Heat energy always moves from a higher temperature () to a lower temperature () until they reach the same temperature.
Problem 3:
Calculate the temperature in Kelvin () if a thermometer reads .
Solution:
Explanation:
To convert Celsius to Kelvin, we use the formula .