Wave Interactions Reflection Absorption Refraction Diffraction Law of Reflection Total Internal Reflection Absorption Refraction Diffraction Interference Constructive Destructive Standing Waves Polarization Resonance

Wave Interactions

Anechoic Chamber An anechoic chamber ("an-echoic" meaning non-reflective, non-echoing or echo-free) is a room designed to completely absorb reflections of either sound or electromagnetic waves. They are also insulated from exterior sources of noise.

Wave Interactions The law of reflection states that the angle of incidence is equal to the angle of reflection.

Wave Interactions

Wave Interactions

STOP! Check for Understanding What is the difference between reflection and refraction? Provide an example of each.

Wave Interactions

Wave Interactions – Interference When two or more waves are at the same place at the same time, the resulting effect is called interference. Waves overlap to form an interference pattern. The waves combine to form a single wave. Constructive interference - when the crest of one wave overlaps the crest of another, their individual effects add together. The result is a wave of increased amplitude. Destructive interference – when the crest of one wave overlaps the trough of another, their individual effects are reduced. The result is a wave of decreased amplitude.

What happens when two crests reach a boat at the same time? The boat rises HIGHER. What happens when two troughs reach a boat at the same time? The boat sinks LOWER. What happens when one crest and one trough reach a boat at the same time? NOTHING! The crest and trough cancel out.

Check for Understanding What is interference? Is interference always a bad thing?

Polarization Polarization is the alignment of transverse waves. Polarizing light filters affect light waves the way the fence affects the waves in the rope.

Standing Waves Although waves usually travel, it is possible to make a wave stay in one place. A wave that is trapped in one spot is called a standing wave. Standing waves are the result of interference. The resultant wave is created by the interference of two waves traveling at the same frequency, amplitude and wavelength but in opposite directions.

Standing Waves In a standing wave, the nodes remain stationary. Antinodes occur halfway between nodes. The largest amplitudes areas are know as antinodes. Standing waves strings of musical instruments, by blowing across the top of a soda bottle.

Nodal Lines A nodal line is a line of minimum amplitude in a moving wave. When 2 waves of similar wavelength meet, and are not in phase, interference lines occur.

Nodal Lines

Interference and Light Interference and diffraction of light support that light is a wave. This means that light waves create anti-nodal lines and nodal lines when light waves interact.

Interference and Light

The Doppler Effect The Doppler effect is the change in observed frequency due to the motion of the source or observer. The Doppler effect is the frequency shift that is the result of relative motion between the source of waves and an observer. Higher frequency: Object approaching Lower frequency: Object receding

The Doppler Effect Example: As the sound of a car's horn passes and recedes from you, the pitch of the horn seems to decrease. Some application: Echolocation (e.g., Submarines, Dolphins, Bats, etc.) Police Radar Weather Tracking

The Doppler Effect http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600::/sites/dl/free/0076659674/78778/Doppler_Nav.swf::Doppler%20Shift%20Interactive MOVING SOUND-GENERATING OBJECT STATIONARY SOUND-GENERATING OBJECT Velocity, v A B Waves are created at point source and radiate outward creating a wave front with the same frequency as that of the source. Wavelengths stay the same As a an object moves towards you the sound waves compress. As an object moves away from you the sound waves lengthen

Scattering Light scattering Occurs when light hits an object with an uneven surface When this happens light is reflected in all directions

Scattering Why is the sky blue? Why are clouds white? This is due to blue wavelengths of light being scatted by the most by the atmosphere as they are the shortest wavelength. Why are clouds white? This is due to the large molecule of water in the clouds scattering all wavelength of light

Scattering

Electromagnetic Spectrum Light is a transverse wave as it can be polarized Light is a wave as diffraction & interference occur in light. Electromagnetic waves do not require a medium. Currently we recognize that there are different types of electromagnetic waves.

Electromagnetic Spectrum The range of wavelength for visible light are 7 x 10-7 m to 4 x 10-7 m

Shadows and Images Shadows and images are produced because light travels in straight lines. If a light source is close to an object it produces a clear shadow.

Shadows and Images When a light source is further away from an object it produces a partial and full shadow. Penumbra is a partial shadow Umbra is a full shadow

Penumbra and Umbra Solar and Lunar eclipses have a Penumbra and an Umbra Although, Penumbras exist in real life it is easier to consider mathematical examples using sharp shadows that do not have a penumbra.

Pinhole camera Image produced is Inverted (upside down) Real (can be projected onto a screen) Usually smaller

Pinhole camera

Pinhole camera

Pinhole camera 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛= ℎ𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑖𝑚𝑎𝑔𝑒 ℎ𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑜𝑏𝑗𝑒𝑐𝑡 = ℎ 𝑖 ℎ 𝑜 OR = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑓 𝑖𝑚𝑎𝑔𝑒 𝑓𝑟𝑜𝑚 ℎ𝑜𝑙𝑒 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑓 𝑜𝑏𝑗𝑒𝑐𝑡 𝑓𝑟𝑜𝑚 ℎ𝑜𝑙𝑒 = 𝑑 𝑖 𝑑 𝑜 ℎ 𝑖 ℎ 𝑜 = 𝑑 𝑖 𝑑 𝑜

Examples We will run through the examples on the board (pages 278-279) Assignment Page 280 # 1-7