wave

Question 1

what is amplitude

Answer 1

max displacement from equilibrium at a point

Question 2

what is frequency

Answer 2

number of oscillations at a point per unit time

Question 3

what is phase difference

Answer 3

how out of sync the oscillations are at two points

Question 4

what is the main difference between a progressive and a stationary wave

Answer 4

progressive transfers energy; stationary stores energy

Question 5

explain how a stationary wave is formed on a string

Answer 5

wave is reflected at fixed end of the string; reflection interferes with original wave; result is a wave with no energy transfer

Question 6

how to find wavelength of standing wave

Answer 6

double the distance between two adjacent nodes

Question 7

what is interference

Answer 7

resultant displacement = sum of individual displacements of two waves at a point

Question 8

what does it mean when two waves are coherent

Answer 8

constant phase difference

Question 9

relationship between intensity and amplitude

Answer 9

intensity proportional to amplitude squared

Question 10

what are the conditions for a minimum in an interference pattern

Answer 10

constant phase difference of 180 degrees

Question 11

what is intensity

Answer 11

power per unit area

Question 12

what are two properties that are unique to EM waves

Answer 12

can travel through a vacuum; all travel at speed c in a vacuum

Question 13

what is meant by a polarised wave

Answer 13

oscillations are in only one direction perpendicular to energy transfer

Question 14

an object is put behind two perpendicular polarising filters; explain why it is not visible

Answer 14

filter 1: light is vertically polarised; filter 2: only horizontal light is let through; so no light gets to our eyes

Question 15

an object is put behind three polarising filters, each at 0, 45, and 90 degrees; explain whether the object is visible

Answer 15

filter 1: light is vertically polarised; filter 2: vertical light is polarised to its 45 degree component; filter 3: 45 degree light is polarised to its horizontal component; so some light gets to our eyes

Question 16

explain how a stationary wave pattern forms in a microwave oven

Answer 16

microwaves reflect off the walls; reflections interfere with original waves; standing wave pattern formed with nodes and antinodes, and no net energy transfer

Question 17

what are the points of max amplitude in a standing wave

Answer 17

antinodes

Question 18

what are the points of min amplitude in a standing wave

Answer 18

nodes

Question 19

what is displacement

Answer 19

distance of a point from equilibrium

Question 20

what are the wavelengths of all the EM waves

Answer 20

micro = 10^-4 m; infrared = 10^-6 m; ultraviolet = 10^-8 m; gamma = 10^-12 m

Question 21

explain how minima and maxima occur in an interference pattern

Answer 21

constructive interference causing maxima where phase diff is 0; destructive interference causing minima where phase diff is 180

Question 22

what is path difference

Answer 22

difference in distance travelled for two waves at a point

Question 23

what is a transverse wave

Answer 23

wave with oscillations perpendicular to energy transfer

Question 24

how to get more diffraction

Answer 24

make gap width equal to wavelength

Question 25

why does amplitude of a circular wave decrease with distance

Answer 25

energy of the wave spreads out

Question 26

what conditions are needed for an interference pattern between two sources

Answer 26

sources must be coherent; and have similar amplitude; and be close together so their waves overlap

Question 27

what is resonance

Answer 27

when frequency of driving force equals natural frequency; this causes increased amplitude of oscillations

Question 28

what is simple harmonic motion

Answer 28

acceleration is proportional to displacement; and acts towards equilibrium