What is Energy? “Energy” is defined as the ability to do work Work is using energy to move something

What are Waves? A wave is a disturbance that transfers energy from place to place. Most waves need a “medium” or substance to travel through Gas, liquids & solids can all be mediums A moving object can transfer energy to a medium, producing waves. Waves travel out in all directions from the disturbance

Mechanical Waves Waves that REQUIRE a medium are called “mechanical waves.” through which to travel Mechanical waves do not carry the medium they travel through with them Waves on the ocean do not move the water molecules with them Molecules stay in place, just “bob” up and down while the energy moves onward Mechanical waves are produced when an energy source causes a medium to vibrate

Types of Waves Mechanical waves are classified by how they move through a medium. Two types of Mechanical Waves 1. Transverse waves 2. Longitudinal waves

Transverse Waves Transverse waves move the medium at a right angle to the direction of the wave Moving a rope up and down, crests & troughs

Examples of Transverse Waves 1. S – Waves (earthquakes) 2. Water waves 3. Light waves, radio waves Microwaves, etc. es/cezar/ariel/ANIMATI ONS/images/wave_movi e.gif

Longitudinal Waves Longitudinal waves move the medium parallel to the direction in which the waves travel Looks like a slinky being “pushed” back and forth Compressions: when the coils or particles are close together Rarefactions: when the coils or particles are farther apart

Examples of Longitudinal Waves 1. P – waves (earthquakes) 2. Sound

Crest trough midpoint Crest: High point in the wave Trough: Low point in the wave Midpoint of wave where the wave is at rest Amplitude Distance from the midpoint to the crest or trough The higher the amplitude the stronger the wave and the more energy it has Properties of waves -

Amplitude Amplitude of transverse waves: height of crest or trough Amplitude of longitudinal waves: how dense the compressions

Wavelength Wavelength is the distance between two identical parts of a wave Crest to crest Trough to trough The energy of a wave depends on the wavelength Shorter wavelengths = more energy

Frequency Number of complete waves that pass a given point in a certain amount of time. If two waves passes by every second, the frequency is 2 waves per second. Frequency is measured in hertz (Hz) so 2 Hertz If 20 waves pass a point in 4 seconds – what is the frequency? 20 waves = 5 Hz 4 sec

Wave Speed Light waves travel faster than sound waves (about a million times faster!) Speed = how far the wave travels in a given length of time Write the formulas below on your notes Speed = Wavelength ∙ frequency Frequency = SpeedWavelength = Speed Wavelength Frequency If you increase the frequency, the wavelength decreases to keep the same wave speed. Higher frequency and shorter wavelength = more energy

Sound Waves: Frequency (Hz) Wavelength (m) Wave Speed (m/s) Sound waves at a concert reach your ears at the same time. Lower notes have long wavelengths, high notes (higher frequency) have shorter wave lengths, but they all have the same wave speed.

Math Practice: 1.A wave has a frequency of 5 Hz. It has a Length of 3 meters. What is the wave speed? 2. A wave has a speed of 100 m/sec. It has a length of 5 meters. What is the frequency? Speed = (Frequency ) (wavelength) Speed = 5 x 3 = 15 m/sec Frequency = Wave Speed wavelength = 100 = 20 Hz 5

3. A wave has a speed of 50 m/sec. It has a frequency of 10 Hz. What is the wavelength? waves pass a point in 10 seconds. What is the frequency of the wave? Frequency = number of waves time = 600 = 60 Hz 10 Wavelength = Wave Speed frequency = 50 = 5 meters 10

Mini-Labs! Station 1- Frequency Station 2- Amplitude Station 3- Speed Station 4- Wavelength AT TABLE Lab on observations about slinky

Electromagnetic Waves Transverse wave that transfers electrical and magnetic energy Moves at the speed of light in a vacuum. (186,000 miles per second) Do not require a medium, so they can travel through the vacuum of space

Electromagnetic Spectrum All electromagnetic waves travel at the same speed, but they have different wavelengths and frequencies. The electromagnetic spectrum organizes the complete range of electromagnetic waves in order of increasing frequency

Electromagnetic or Light Energy Light behaves like waves and packets of energy (photons) at the same time Increased frequency = shorter wavelength and more energy.

Put the stars and underlines on your notes

Electromagnetic Spectrum Made up of: 1. Radio waves-radio, tv, cell phones 2. Microwaves – ovens, communications, RADAR 3. Infrared rays-heat lamps, infrared cameras 4. Visible light-colors, light we see 5. Ultraviolet rays-rays from the sun that cause sunburn 6. X-rays-medicine, engineering 7. Gamma rays-some radioactive materials

Light Energy White light can be separated into the visible color spectrum as the waves are “bent” or refracted through a prism or through water drops. Red wavelengths bend the least and blue bend the most. That is why red is on top of a rainbow. ROY G BIV Red, Orange, Yellow, Green, Blue, Indigo, Violet

Heat Heat is thermal energy moving from a warmer object to a cooler object. The energy depends on the movement of the atoms Atoms move faster = higher heat energy Atoms move slower = lower heat energy Class Discussion: Does temperature rise at the same rate for everything? Hot sand & cold water.

Specific Heat Amount of heat needed to increase the temperature of a specific substance. The temperature does not increase at the same rate for everything

Heat Transfer

1. ________________transfer of heat energy through _________________Molecules move faster as they heat and bump into other molecules causing them to move. Conduction: direct contact. Heat Transfer – 3 types

2. _______________transfer of heat ____________________ As molecules heat and move faster they move apart. This makes them less dense and they rise. When they cool off they move closer making them more dense and they sink. Convection: in gases and liquids

3. ______________transfer of heat energy though space as electromagnetic waves. Infra red waves are felt as heat. All electromagnetic waves are forms of radiation. Radiation:

Heat Transfer Worksheet Provide an example of each type of heat transfer in the following situations. Cooking on a stoveVolcano erupting In a house