Waves Flashcards
What are waves and what do they do?
Transfer energy from one place to another
Transfer information
There are different types of waves
What are the different types of waves?
Sound waves, Water waves, Springs and Earthquakes are all examples of Mechanical waves which are vibrations that can travel through a medium
Light waves, Radio waves and Microwaves are examples of electromagnetic waves which can travel through a vacuum
What are longitudinal waves?
Vibrate parallel to direction of energy transfer of the waves
Eg sound
When an object vibrates in air it makes the air around it vibrate as it pushes and pulls on the air - the oscillation is the sound waves
What are transverse waves?
Vibrate perpendicular (at right angles) to direction waves transfer energy
Eg light
All electromagnetic waves are transverse
Mechanical waves can be transverse or longitudinal - water waves are transverse
How do we measure waves?
- Amplitude - height of wave above position of rest
- Wavelength - lambda - distance between two corresponding points on waves usually trough or peak = metres
- Frequency - how many waves pass by a point every second - hertz
What is the wave equation?
Relates speed of wave to its frequency and wavelength Wave speed (m/s) = frequency (Hz) x wavelength (m) V = f x ¥
What is the equation for period?
Period = 1➗frequency T= 1➗f
What is reflection?
All waves can be reflected
Reflection occurs when a wave changes direction at a boundary between two different mediums
When reflected waves always obey law of reflection
All angles measured to the normal
What happens when plane waves reflect off a surface?
Frequency and wavelength remain unchanged
What is refraction?
Refraction occurs when wave changes direction as its speed changes
When a wave refracts there is always some reflection
Slowing down it refracts towards the normal
Speeding up it refracts away from the normal
Water waves refract when a change in depth
What is the law of reflection?
Angle of incidence = angle of reflection
I=r
Explain the electromagnetic spectrum?
Electromagnetic spectrums are electric and magnetic disturbances that transfer energy from one place to another
Energy transferred depends on wavelength of waves
Long - radio waves- as long as 10km
Short - x rays and gamma rays - 0.000000000001mm
The speed of electromagnetic waves?
Travel at speed of light: 3000000 m/s
What is the frequency of mobile phone waves?
900 million Hz
Examples of wavelength?
Radio - wavelength 10(3) - size of buildings - frequency 10(4)-(8) - temperature 0->0.5k
Microwave - 10(-2) - honey bee - 10(8)-(12) - 0.5->1k
Infra red - 10(-5) - pinpoint - 10(12) - 1->100k
Visible - 0.5 x 10(-6) - bacteria, protozoan - 10(15) - 100->10000k
Ultra violet - 10(-8) - molecules - 10(16) - 10000->5 millionk
X-ray - 10(-10) - atoms - 10(18) - 5->10 millionk
Gamma rays - 10(-12) - atomic nuclei - 10(20) - 10 millionk+
