Waves Flashcards
What is a Wave
Disturbance that propagates through space and time
Transfer of energy (Not matter)
How Does Propagation of Disturbance Work
Disturbance is created in medium, creates domino effect = Disturbance travels through medium
What are the Two Types of Waves
Mechanical Waves
Electromagnetic Waves
What are Electromagnetic Waves
Doesn’t need medium, travels through vacuum
Eg. Light
What are Mechanical Waves
Waves that need medium to travel through
Is made up of transverse and longitudinal waves
What is a Medium
Substance that waves travel / propagate through
What is a Transverse Wave
Where the oscillation of wave is perpendicular to the motion of wave
What is a Longitudinal Wave
Where the oscillation of wave is in direction to the motion of wave
What is amplitude
Maxiumum displacement from rest position
What is crest
Maximum positive distance from rest position
What is trough
Maximum negative distance from rest position
What is phase
Two corresponding points in displacement from rest position, and direction of motionQ
What is wavelength
Distance between two consecutive points in phase
What is ray diagrams
Shows direction of propagation of wave
- Rays always perpendicular to wave fronts
What is period
Time in seconds taken for 1 complete rotation / wavelength
What is frequency
Number of rotations / wavelengths in 1 second
- Measured in Hz
What is wavefront
Connects all locations where wave has same phase
What is compression
Region of higher than normal pressure
What is rarefaction
Reigion of lower than normal pressure
What is velocity
The speed the graph is moving
What is wavelength (Longitudinal)
Distance between two successive compressions / rarefactions
What is intensity
Energy / Power per unit area
Moving further from source = Power spread over larger area = Reduces intensity
What is inverse squared law
Assuming waves spread spherically, obeys laws
Wave propagates distance, r, away from source, intensity of wave decreases by r^2
So intensity inversely proportional to distance^2
What are Wave-Front Diagrams
Depicts changes in wavelength
Also good to show diffraction and spreading of waves
What Does Speed of Sound Wave Depend on (The Medium)
Density (Higher density = Lower speed),
Elasticity (Higher elasticity = Higher speed),
Temperature (Higher temperature = Higher speed)
What is Refraction
Wave transmitted through boundary from 1 medium to another, with diff. velocity & wavelength, wave travels in different direction to original wave
What is the Refraction Application of Seismic Waves
Phenomena that Earth’s outer core is liquid, as transverse shear waves are not detected in it
Longitudinal pressure waves are refracted by molten core, suggesting it is liquid (Waves from Earthquake, both detected near epicentre)
What is the Behaviour After Refraction if the Wave Increases in Speed in the New Medium
Refracted angle bigger than incident angle
Wavelength is bigger in new medium
So bends away from the normal
What is the Behaviour After Refraction if the Wave Decreases in Speed in the New Medium
Incident angle bigger than refracted angle
Wavelength smaller in new medium
Bends towards normal
What is Reflection
Wave changes direction at boundary between two mediums, returning to medium it starts in
What is Behaviour After Reflection
Wavelength doesn’t change
Reflected angle = Incident angle
What is Changes in Phase in Reflection
If wave reflected from fixed point, is closed end, so phase is inverted
- Some energy absorbed by post = Reflected amplitude lower
If wave reflected from open end, no phase change
What is the Application of Echoes in Reflection
Sound wave reflected on wall, returns to source after delay
