Waves

Question	Answer
Wave Speed Equation	Wave speed = frequency x wavelength Image: Wavespeed+Triangle (binary/octet-stream)
Velocity Equation	Velocity = frequency x λ Image: Veloccity+Trangle (binary/octet-stream)
Transverse Waves	Oscillate at a right angle to the direction of the wave (Eg. EM waves)
Examples of transverse waves	- electromagnetic waves (light) - ripples and waves in water - a wave on a string
Longitudinal Wave	Oscillate parallel to the direction of the wave (Eg. mechanical)
Examples of longitudinal waves	-sound waves in air (ultrasound) - shock waves (some seismic waves)
When light enters an optically denser medium it refracts..	Towards the normal
When light enters an optically less dense medium it refracts..	Away from the normal
Conditions for TOTAL INTERNAL REFLECTION:	The angle of incidence must be greater than the critical angle -Light must travel from an optically dense medium to a less optically dense medium.
Cladding	Prevents information to cross over from one fibre making it secure. Slightly lower refractive index compared to core making it totally internally reflect.
Optical Fibres (ADVANTAGE)	-More information - More secure - Little energy lost (Copper loses energy through heat loss)
Optical Fibres (DISADVANTAGE)	-Impurity -Modal dispersion -Spectral dispersion
Stationary Waves	Produced when two waves of the same frequency, amplitude and constant phase difference travel in opposite directions through the same medium.
Diffraction	It's the spreading out of waves when they pass through an opening around an obstacle which is comparable in size to their wavelength.
List the EM spectrum	Radio Waves Micro waves Infra red Visible Light Ultra Violet (UV) Xrays Gamma Rays
Electromagnetic waves	They do not travel through a medium but can travel through a vacuum. They travel through space at the speed of light (Eg. Radio, Infrared, UV)
Radio waves	~Used to broadcast TV and radio signals ~Long-wave radio can be transmitted around the world. ~ Radio waves carry few or no dangers because of their low frequency and long wavelength.
Micro waves	~Used for satellite communication and mobile phones ~Microwaves can cause heating ~Microwaves can burn human body cells, and are therefore a danger.
Infrared waves	~Used as a heat detecting radiation ~The higher the temperature the brighter the image appears, used by police ~Can also heat cells by causing them to vibrate, -IR has higher frequency so can cause skin burns.
Visible light	~Visible light is required to see objects ~Visible light is reflected off objects ~Visible light is used in photography in a similar way to the eye ~Can cause blindness in extreme cases.
Ultraviolet	~UV is absorbed by fluorescent ~UV is used to detect forged bank notes with no fluorescent markings ~Can also be used to disinfect water ~High frequency means ionising so can mutate cells cause cancer and eye damage.
X-Rays	~ X-rays in hospitals not absorbed by denser materials so shows bone structure ~Also used in airports to scan baggage ~ More ionising, can cause cell mutation and cancer. more penetrative.
Gamma rays	~Ionising radiation, can cause cancer and mutations ~Can also be used to sterilise food ~Can treat cancer by killing cancerous cells ~ Highest frequency EM wave.
What is amplitude	The maximum displacement of a point on the wave from its undisturbed position.
Wavelength	The distance between the same point on two adjacent waves.
Frequency	The number of complete waves passing a certain point per second it is measured if Hertz ( 1 Hz is 1 waver per seconds).
Period of a wave calculation	period (s) = 1 / frequency (Hz) T = 1 / f
What is refraction?	- Waves changing direction at a boundary -When a wave crosses a boundary between materials at an angle it changes direction -The amount refracted depends on how much the waves speed up/down. this depends on the density.
The law of reflection	The angle of incidence is ALWAYS equal to the angle of reflection.
What is refraction	When light changes direction as it goes from one medium to another.

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	Created by Jacob RAMZAN almost 3 years ago