4.4- WAVE PROPERTIES 2

Question 1

What do waves do when they meet?

Answer 1

pass through each other

Question 2

What happens at the point where waves meet?

Answer 2

combine for an instant before they move apart

Question 3

What is the combining effect at the point where waves meet called?

Answer 3

superposition

Question 4

What does the principle of superposition state?

Answer 4

when two waves meet, total displacement at a point is equal to sum of individual displacement at that point

Question 5

What is created when a crest meets a crest?

Answer 5

supercrest

Question 6

What is a supercrest?

Answer 6

two waves reinforce each other

Question 7

What is created when a trough meets a trough?

Answer 7

supertrough

Question 8

What is a supertrough?

Answer 8

two waves reinforce each other

Question 9

What is the resultant displacement when a crest meets a trough of the same amplitude?

Answer 9

zero- two waves cancel each other out

Question 10

What is the resultant called when a crest meets a trough with different amplitudes?

Answer 10

resultant called a minimum

Question 11

How can stationary waves be formed on a rope?

Answer 11

if two people send waves continuously along a rope from either end

Question 12

What are the two sets of waves when a stationary wave is formed from two people sending waves continuously along a rope called?

Answer 12

progressive waves

Question 13

Why are the two waves formed when two people send waves continuously along a rope called progressive waves?

Answer 13

to distinguish them from stationary waves

Question 14

What do stationary waves do along a rope?

Answer 14

combine at fixed points along the rope to form points of no displacement or nodes along the rope

Question 15

How many degrees are the two sets of waves out of phase at each node? (stationary waves on a rope)

Answer 15

at each node, the two sets of waves are always 180 degrees out of phase

Question 16

What happens as the two sets of waves are always 180 degrees out of phase at each node?

Answer 16

they cancel each other out

Question 17

What kind of waves does a vibrating dipper on a water surface send out?

Answer 17

circular waves

Question 18

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?

Answer 18

where crest from one dipper meets trough from other dipper

Question 19

How are points of cancellation seen when two sets of circular waves are produced? (water waves in a ripple tank)

Answer 19

gaps in wavefronts

Question 20

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?

Answer 20

where crest from one dipper meets crest from other dipper, or where trough from one dipper meets trough from other dipper

Question 21

Why does cancellation and reinforcement occur at fixed points? (water waves in a ripple tank)

Answer 21

as waves continuously passing through each other at constant frequency + at constant phase difference

Question 22

What is it called when cancellation and reinforcement occurs at fixed points?

Answer 22

interference

Question 23

Why do coherent sources of waves produce an interference pattern where they overlap?

Answer 23

as they vibrate at the same frequency with a constant phase difference

Question 24

What would happen to interference pattern if coherent waves’ phase difference is changed at random?

Answer 24

points of cancellation + reinforcement would move about at random, + no interference pattern would be seen (waves no longer coherent)

Question 25

What can a microwave transmitter + receiver be used to demonstrate?

Answer 25

reflection, refraction, diffraction, interference, and polarisation of microwaves

Question 26

What does the microwave transmitter do when demonstrating reflection, refraction, diffraction, interference and polarisation of microwaves?

Answer 26

produces microwaves of wavelength 3.0cm

Question 27

What can the microwave receiver be connected to? (tests using microwaves)

Answer 27

suitable meter, which gives measure of intensity of microwaves at receiver

Question 28

#1 where is the receiver placed? (tests using microwaves)

Answer 28

in path of microwave beam from transmitter

Question 29

#2 after placing the receiver in the path of the transmitter, what do you do? (tests using microwaves)

Answer 29

move receiver gradually away from transmitter + note receiver signal decreases with distance from transmitter

Question 30

What does the receiver signal decreasing with distance from the transmitter show? (tests using microwaves)

Answer 30

microwaves become weaker as they travel away from the transmitter

Question 31

#3 tests using microwaves

Answer 31

place metal plate between transmitter + receiver to show microwaves cannot pass through metal

Question 32

#4 tests using microwaves

Answer 32

using two metal plates to make a narrow slit + show that receiver detects microwaves that have been diffracted as they pass through the slit

Question 33

How to show less diffraction from #4? (tests using microwaves)

Answer 33

if slits made wider, less diffraction occur

Question 34

How to show cancellation and reinforcement? (test using microwaves)

Answer 34

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