Physics Waves

Waves The components of all waves include: Wavelength Amplitude Frequency Period Velocity Waves transfer energy over distances. An example would be heat from the Sun or an earthquake. No mass is being transferred, just energy.

Wavelength and Amplitude (λ) Wavelength Amplitude Crest Time Trough Also, one wavelength () http://www.howlaserswork.org/light-physics/wavelength-frequency-and-amplitude/

Frequency Frequency is the number of waves passing by a particular point in a given length of time. The number of waves per second is measured in Hertz (Hz). http://www.casellausa.com/en/images/help/sine_waves.jpg

Period and Speed The period is the length of time it take for one wave to pass. The speed of the wave can be calculated by: •Speed = Distance traveled by the wave Time of travel or •Speed = Wavelength x Frequency

Calculating Wave Speed If a boy blows his trumpet, how fast will the sound travel to his friends who are 170 meters away and who hear the sound 0.5 seconds later? Speed = Distance / Time Speed = 170 m / 0.5 s Input: Concept in calculating speed is also covered in Session 7. Speed = 340 m/s

Calculating Wave Speed If the wavelength of the wave generated in a slinky is 0.5 m and the frequency of the wave is 7 Hz, what is the wave speed? Speed = Wavelength x Frequency Speed = 0.5 m x 7 Hz Input: Hertz is defined on Slide 5 Speed = 3.5 m/s Hz = Hertz = waves/sec

Longitudinal vs. Transverse Waves Longitudinal Wave (Compression wave) Transverse Wave Slinky waves can be made by vibrating the first coil back and forth in either a horizontal or vertical direction. http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l1a.html

Longitudinal Waves Particle displacement is parallel to the direction of wave propagation. Input: Suggested material: Slinky http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

Sound Waves Sound waves are longitudinal waves. Sound waves must travel through a medium. There is no sound in a vacuum. Sound waves vibrate the eardrum. The vibrations pass through the middle ear bones to the cochlea. In the cochlea, the vibrations bend tiny hairs which convert the sound waves to nerve impulses. Input: http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l2d.html

Transverse Waves Particle displacement is perpendicular to the direction of wave propagation. http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

Light Waves Light travels in transverse waves. Light is composed of little packets of energy called photons, which do not need to travel through a medium. Light can travel through a vacuum. Visible light is the colors of the visible spectrum: Red, Orange, Yellow, Green, Blue, Indigo and Violet A mnemonic device to remember the colors is ROY G BIV. Visible light is only one portion of the electromagnetic spectrum of energy waves.

Electromagnetic Spectrum Input: Suggested Activity: Spectroscope Lab: Have the group read and discuss the activity. The lab requires too many supplies to complete at the session, but encourage the participants to complete in their classrooms. 15 http://www.lakeeriewx.com/CaseStudies/RadarSunSpikes/EM_Spectrum3-new.jpg

Vision involves two main components: Vision and Light Waves Vision involves two main components: Focusing the light that enters the eye onto the retina. This is accomplished by the curved cornea and the lens. Activation of the photoreceptors in the retina to transmit nerve impulses to the brain. The is carried out by the rods and cones.

Water Waves Water waves involve a combination of both longitudinal and transverse motions As a wave travels through the water, the particles travel in clockwise circles. http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html

Seismic Waves P waves are longitudinal. S waves are transverse. Surface waves are both longitudinal and transverse. Tsunamis are water surface waves, therefore they are both longitudinal and transverse.

Waves and Matter Waves are the transmission of energy. When coming in contact with matter, waves undergo: Reflection – bouncing back Refraction – bending Absorption – passing into the matter Transmission – passing through the matter

Reflection of Waves Reflected waves are simply those waves that are neither transmitted nor absorbed, but are bounced back from the surface of the medium they encounter. When a wave approaches a reflecting surface, such as a mirror, the wave that strikes the surface is called the incident wave. The one that bounces back is called the reflected wave. An imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface is called the normal.

Normal Normal http://laser.physics.sunysb.edu/~amy/wise2000/websites/Mirror348.jpg

The Law of Reflection Objects can be seen by either the light they emit or by the light they reflect. Reflected light obeys the law of reflection, that the angle of incidence equals the angle of reflection. The Law of Reflection also applies to water waves, sound waves, and billiard balls as well. Angle I = Angle R http://www.glenbrook.k12.il.us/gbssci/Phys/mmedia/optics/lr.html

Law of Refraction: Snell’s Law Snell's law gives the relationship between angles of incidence and refraction when light passes from one transparent medium to another. Light bends according to Snell's law which states: n1 sin θ 1 = n2 sin θ 2 n1 = the refractive index of substance 1 θ1 = the angle of incidence in substance 1 n2 = the refractive index of substance 2 θ2 = the angle of refraction in substance 2

Refraction Light twists inward when entering medium of higher index of refraction.  Light twists outward when entering medium of lower index of refraction. http://sol.sci.uop.edu/~jfalward/refraction/refraction.html