5.1 & 5.2 Waves Flashcards
What is the relationship between stationary waves and length
The longer the length of string, the lower the frequency.
What is the relationship between stationary waves and mass per unit length
The larger the mass per unit length the lower the frequency. For the same length string waves travel slower through a heavier string so frequency is reduced
Relationship with tension in stationary waves
The higher the tension in the string, the higher the frequency. This is because waves travel quicker down a string with higher tension
How are stationary waves formed?
A stationary wave is formed when two progressive waves each with the same frequnecy, wavelength and moving in opposite directions, interfere with one another. This creates a wave which doesn’t transfer energy from one place to another.
What is superposition
Where the displacements of two waves are combined as they pass each other the resultant displacement is the sum of each waves amplitude
What is a wavefront
A surface which is used to represent the points of a wave which have the same phase
What is phase
The position of a certain point on a wave cycle. This can be measured in radians degrees or fractions of a cycle
What is phase difference
How far a wave lags behind another
What is path difference
The difference in distance travelled by two waves
What is a coherent light source
A light source that has the same frequency and wavelength and a fixed phase difference
What is constructive interference
Occurs when two waves are in phase and so their displacements are added
What is destructive interference
Occurs when the waves are completely out of phase and so displacements are subtracted
What conditions must there be for two waves to be in phase
Two waves are in phase if they are both at the same point of the wave cycle, meaning they have the same frequency and wavelength and their phase difference is an integer multiple of 360(2pi radians). They are not required to have the same amplitude
What conditions are there for two waves to be completely out of phase
They must be coherent waves and their phase difference is an odd multiple of 180 (pi radians)
What equation shows the relationship between phase difference and path difference of two coherent waves
Path difference = wavelength/2pi x phase difference
What energy is transferred by a stationary wave
None
When a stationary wave is formed what happens when the waves meet in phase
Constructive interference occurs so antibodies are formed which are regions of maximum displacement
What happens when sationary waves are formed and the two waves meet out of phase
Destructive interference occurs and nodes are formed, which are regions of no displacement
What happens if the path difference is a multiple of wavelength
The waves will be in phase and we will see constructive interference
What happens if the path difference is a whole number plus a half multiplied by wavelength
They will be completely out of phase
What is monochromatic
The light is all the same wavelength (lasers)
What must happen for a diffraction pattern
Wavelength to be roughly the same as the slit width
What are the light and dark fringes on a diagram caused by
The light fringes are caused by constructive interference and the dark fringes are caused by destructive interference.
Why is white light different to a laser
White light is made up of all the visible colours of light it’s not monochromatic
