Unit 11: Waves

 When waves hit a flat mirror they bounce off at a predictable angle.  Reflection always makes a V.  Law of Reflection:  Incident =  reflection or  In =  Out

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 Refraction – the bending of light that occurs when a light wave passes through a boundary between two media  When light refracts it BENDS, CHANGES SPEED and WAVELENGTH  The slower the medium, the sharper the angle of refraction with normal.  Slower/steeper  Faster/further

(Light must come in at an angle to be refracted)

- Air has the smallest (most fast) refraction number -Diamonds have the highest (slowest) refraction number

Which ray is correct if fused quartz is faster than X? Which ray is correct if fused quartz is slower than X? Which ray is correct if X and quartz have the same optical density? Which ray is impossible?

 Diffraction – waves spread out into the region behind an obstacle  Example: Light passing through a slit in paper.

 Whole Wavelength Shift of a wave. The two waves reinforce each other.

 1/2 λ difference the two waves cancel each other out. 

 Resonance – Building up of energy by adding small amounts of energy in time with the natural frequency of an object. Resonance Breaking glass

 As an object moves, the waves are compressed in the direction of the motion and expanded in the direction away from the motion.  Sound – higher or lower pitch  Light- blue or red color shift

 A single disturbance moving through a medium from one location to another location  Wave Pulse Wave Pulse

 Visible Light is electromagnetic radiation that can be detected by our eyes.  However, visible light only makes up a tiny portion of the electromagnetic spectrum.

 The electromagnetic (EM) spectrum consists of multiple types of radiation that are classified according to the amount of energy they contain.  Some types of electromagnetic radiation energy are gamma rays, x-rays, microwaves, ultraviolet waves, infrared radiation, visible light, and radio waves.

 As the frequency of a wave increases (and the wavelength decreases) the energy of the wave increases.

 All EM radiation moves at the same rate, we call it the speed of light.  The speed of light is about 3.0 x 10 8 m/s  Electromagnetic radiation is slowed slightly in the Earth’s atmosphere, but not enough to measure it with a number less than 3.0 x 10 8 m/s.

 If this picture represents the reflection of a mirror and j is 60 , what angle is r?

 List mediums a, b, and c in order of refraction from slowest to fastest.

 Which is an example of constructive interference?  Which is an example of destructive interference?

 You hit one tuning fork and another tuning fork also starts to ring. What do these two forks have in common?

 How does the sound of the car compare from person A to person B?

 Is this galaxy getting closer to or further from earth? How do you know?

 This Equation was Einstein’s greatest theory. It states that Energy can turn into mass and that mass can turn into energy.  It is often called the energy/mass equivalency.  E=mc 2  E is energy measured in JOULES  M is mass measured in KG  C is the speed of light (3 x 10 8 m/s)

 If a 7.2 x kg unicycle is accelerated to the speed of light, how much energy would it create? E = mc 2 E = ? m = 7.2 x kg c = 3 x 10 8 m/s E = mc 2 = 7.2 x kg x (3 x 10 8 m/s) 2 = 6.48 x J

o If 30,000J of energy is converted to mass, how much mass would it create? E = mc 2 E = 30,000 J m= ? kg c = 3 x 10 8 m/s E = mc 2 m = E/c 2 = 30,000 J /(3 x 10 8 m/s) 2 = 3.3 x kg

 How much energy is equivalent to a mass of a stick of butter (0.100 kg)?  The Sun converts mass to energy at such a rate that it produces 3.9 x J of energy every second. How much mass is converted to energy each second to produce this energy?