Electromagnetic Waves Electromagnetic Waves EM Waves are TRANSVERSE

Electromagnetic Waves Calculate the wavelength of a radio wave traveling through outer space with

Aim: How do waves interact with different boundaries? HW: WS

Two types of wave sources Point Source • One point that oscillates – Like

$Diffraction • Diffraction is the bending of a wave around a barrier Know any$

Ripple tank “A way to show wave behaviors” Point source Plane wave Angled Reflection

$Point Source Plane wave Angled Reflection Diffraction around a corner$

Single Slit Double slit Constructive interference Doppler effect Your own: Towards: -High frequency -

Huygen’s Principle • A wave front is made up of WAVELETS • Each WAVELET

Huygen’s Principle • Barrier blocks part of a WAVE FRONT • Remaining WAVELETS make

$Single Slit Diffraction • A small opening, or a SLIT, is also an obstacle$

$SINGLE SLIT DIFFRACTION • When light is diffracted, the bent light waves interfere with$

$More point sources diffracting at once • How does the amount of diffraction change$

$When Waves Meet A Boundary… 1. Reflect 2. Bend Around 3. Refract$

SUMMARY • How does light behave when it meets an obstacle? • How does

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Electromagnetic Waves • Electromagnetic Waves (EM Waves) are TRANSVERSE WAVES • EM Waves DO NOT require a medium • EM WAVES are radiated by ALL objects at the SPEED OF LIGHT • Speed of Light in vacuum = c = 3 x 108 m/s

Electromagnetic Waves Calculate the wavelength of a radio wave traveling through outer space with a frequency of 5 x 104 Hz? Does this wavelength make sense on our table?

Aim: How do waves interact with different boundaries? HW: WS

Two types of wave sources Point Source • One point that oscillates – Like a child bobbing in the pool. – Produce circular waves Plane Source • An extended (rectangular) source that oscillates. – Produce plane waves

$Diffraction • Diffraction is the bending of a wave around a barrier Know any$

Diffraction • Diffraction is the bending of a wave around a barrier Know any examples? – Consider a door cracked open, what shape does the light make? • If it didn’t bend, it would be a straight column • As you can see the light ‘fans out’ after it passes through the barrier

Ripple tank “A way to show wave behaviors” Point source Plane wave Angled Reflection Diffraction around a corner • Single slit • Double slit • Doppler effect • • Try creating each of the different wave behaviors in your tank.

$Point Source Plane wave Angled Reflection Diffraction around a corner$

Point Source Plane wave Angled Reflection Diffraction around a corner

Single Slit Double slit Constructive interference Doppler effect Your own: Towards: -High frequency - shorter wavelength Away: -Lower frequency - longer wavelength Motion of source

Huygen’s Principle • A wave front is made up of WAVELETS • Each WAVELET is a POINT SOURCE of circular waves • WAVE RAYS are lines PERPENDICULAR to wave fronts that show wave travel DIRECTION

Huygen’s Principle • Barrier blocks part of a WAVE FRONT • Remaining WAVELETS make a shorter WAVE • WAVE RAYS are BENT around CORNERS

$Single Slit Diffraction • A small opening, or a SLIT, is also an obstacle$

Single Slit Diffraction • A small opening, or a SLIT, is also an obstacle • The amount of diffraction depends on the slit width – WIDE Slit LESS Diffraction – NARROW Slit MORE Diffraction

$SINGLE SLIT DIFFRACTION • When light is diffracted, the bent light waves interfere with$

SINGLE SLIT DIFFRACTION • When light is diffracted, the bent light waves interfere with each other CONSTRUCTIVELY and DESTRUCTIVELY • This results in a PATTERN OF LIGHT AND DARK BANDS Graph of Pattern Actual Pattern

$More point sources diffracting at once • How does the amount of diffraction change$

More point sources diffracting at once • How does the amount of diffraction change as the slits becomes smaller?

$When Waves Meet A Boundary… 1. Reflect 2. Bend Around 3. Refract$

When Waves Meet A Boundary… 1. Reflect 2. Bend Around 3. Refract

SUMMARY • How does light behave when it meets an obstacle? • How does slit width correlate to the amount of diffraction? • If diffracted light were shown on a screen, what would you see? – How is it accomplished?