4.4- WAVE PROPERTIES 2 Flashcards
What do waves do when they meet?
pass through each other
What happens at the point where waves meet?
combine for an instant before they move apart
What is the combining effect at the point where waves meet called?
superposition
What does the principle of superposition state?
when two waves meet, total displacement at a point is equal to sum of individual displacement at that point
What is created when a crest meets a crest?
supercrest
What is a supercrest?
two waves reinforce each other
What is created when a trough meets a trough?
supertrough
What is a supertrough?
two waves reinforce each other
What is the resultant displacement when a crest meets a trough of the same amplitude?
zero- two waves cancel each other out
What is the resultant called when a crest meets a trough with different amplitudes?
resultant called a minimum
How can stationary waves be formed on a rope?
if two people send waves continuously along a rope from either end
What are the two sets of waves when a stationary wave is formed from two people sending waves continuously along a rope called?
progressive waves
Why are the two waves formed when two people send waves continuously along a rope called progressive waves?
to distinguish them from stationary waves
What do stationary waves do along a rope?
combine at fixed points along the rope to form points of no displacement or nodes along the rope
How many degrees are the two sets of waves out of phase at each node? (stationary waves on a rope)
at each node, the two sets of waves are always 180 degrees out of phase
What happens as the two sets of waves are always 180 degrees out of phase at each node?
they cancel each other out
What kind of waves does a vibrating dipper on a water surface send out?
circular waves
When two sets of circular waves are produced with a vibrating dipper on water surface and pass through each other continuously, how are points of cancellation created?
where crest from one dipper meets trough from other dipper
How are points of cancellation seen when two sets of circular waves are produced? (water waves in a ripple tank)
gaps in wavefronts
When two sets of circular waves are produced with a vibrating dipper on water surface and pass through each other continuously, how are points of reinforcement created?
where crest from one dipper meets crest from other dipper, or where trough from one dipper meets trough from other dipper
Why does cancellation and reinforcement occur at fixed points? (water waves in a ripple tank)
as waves continuously passing through each other at constant frequency + at constant phase difference
What is it called when cancellation and reinforcement occurs at fixed points?
interference
Why do coherent sources of waves produce an interference pattern where they overlap?
as they vibrate at the same frequency with a constant phase difference
What would happen to interference pattern if coherent waves’ phase difference is changed at random?
points of cancellation + reinforcement would move about at random, + no interference pattern would be seen (waves no longer coherent)
What can a microwave transmitter + receiver be used to demonstrate?
reflection, refraction, diffraction, interference, and polarisation of microwaves
What does the microwave transmitter do when demonstrating reflection, refraction, diffraction, interference and polarisation of microwaves?
produces microwaves of wavelength 3.0cm
What can the microwave receiver be connected to? (tests using microwaves)
suitable meter, which gives measure of intensity of microwaves at receiver
1 where is the receiver placed? (tests using microwaves)
in path of microwave beam from transmitter
2 after placing the receiver in the path of the transmitter, what do you do? (tests using microwaves)
move receiver gradually away from transmitter + note receiver signal decreases with distance from transmitter
What does the receiver signal decreasing with distance from the transmitter show? (tests using microwaves)
microwaves become weaker as they travel away from the transmitter
3 tests using microwaves
place metal plate between transmitter + receiver to show microwaves cannot pass through metal
4 tests using microwaves
using two metal plates to make a narrow slit + show that receiver detects microwaves that have been diffracted as they pass through the slit
How to show less diffraction from #4? (tests using microwaves)
if slits made wider, less diffraction occur
How to show cancellation and reinforcement? (test using microwaves)
use narrow metal plates with to make a pair of slits
direct transmitter at slits + use receiver to find points of cancellation + reinforcement, where microwaves from two slits overlap
