Waves

Question 1

What is a progressive wave?

Answer 1

an oscillation that travels through space transmitting energy from one place to another

Question 2

In what direction are the oscillations to the direction of energy transfer in transverse waves?

Answer 2

perpendicular

Question 3

In what direction are the oscillations to the direction of energy transfer in longitudinal waves?

Answer 3

parallel

Question 4

Define displacement:

Answer 4

the distance from the equilibrium position in a particular direction

Question 5

Define amplitude:

Answer 5

the maximum displacement of a wave

Question 6

Define wavelength:

Answer 6

the distance between 2 adjacent points on a wave that are oscillating in phase

Question 7

Define period:

Answer 7

the time taken for the wave to move a distance of one whole wavelength

Question 8

Define frequency:

Answer 8

the number of wavelengths passing through a point per unit time

Question 9

Define wave speed:

Answer 9

distance travelled by wave per unit time

Question 10

What is the relationship between period and frequency?

Answer 10

f=(1/T)

Question 11

What is phase difference?

Answer 11

the fraction of an oscillation between two oscillating particles

Question 12

What is the phase difference of 1 wavelength?

Answer 12

2π

Question 13

When does reflection occur?

Answer 13

when a wave changes direction at a boundary between two different media, remaining in the original medium

Question 14

When does refraction occur?

Answer 14

when a wave changes direction as it changes speed when it passes from one medium to another

Question 15

What is diffraction?

Answer 15

the spreading of a wave when it passes through a narrow gap or around an obstacle

Question 16

Within reflection what are the incident and reflected waves always in the same?

Answer 16

plane

Question 17

Within reflection what things are equal to each other?

Answer 17

angle of incidence and reflection

Question 18

Within refraction what remains constant?

Answer 18

frequency of the refracted waves

Question 19

What changes within refraction?

Answer 19

the speed and therefore wavelength of the refracted wave

Question 20

What does not change within diffraction?

Answer 20

speed, wavelength and frequency

Question 21

When is there significant diffraction?

Answer 21

width of the gap is similar to the wavelength of the incident wave

Question 22

Where does a plane polarised wave oscillate?

Answer 22

in one plane only

Question 23

How can you plane polarise light?

Answer 23

pass it through a polarised filter

Question 24

Define intensity:

Answer 24

the radiant power passing at right angles through a surface per unit area

Question 25

Why does intensity from a point source of power P decrease with distance from the source?

Answer 25

the power spreads over a larger surface area

Question 26

What is intensity directly proportional to?

Answer 26

amplitude squared

Question 27

Which type of EM waves have the shortest wavelength?

Answer 27

gamma waves

Question 28

Which type of EM waves have the longest wavelength?

Answer 28

radio waves

Question 29

What can all EM waves travel through?

Answer 29

a vacuum

Question 30

What is the speed of EM waves?

Answer 30

3 x 10^8

Question 31

What type of wave are EM waves?

Answer 31

transverse

Question 32

What do all EM waves consist of?

Answer 32

oscillating magnetic and electric fields at right angles to each other

Question 33

How do you produce plane polarised waves with the electric field oscillating in the vertical plane?

Answer 33

pass microwaves from a microwaves transmitter through a metal grill towards a microwave receiver

Question 34

When polarising microwaves what happens when the metal grille is horizontal?

Answer 34

vertical plane polarised waves are transmitted through

Question 35

When polarising microwaves what happens when the metal grille is vertical?

Answer 35

vertically plane polarised waves are absorbed by the free electrons within the metal rods of the grille therefore there is almost no transmission

Question 36

Define refractive index:

Answer 36

speed of light in a vacuum divided by the speed of light in the material (c/v)

Question 37

What is the law of refraction?

Answer 37

n1sin1=n2sin2

Question 38

When is there no refraction?

Answer 38

when total internal refraction of the light occurs at the boundary between 2 transparent materials

Question 39

What happens when there is no refraction due to total internal reflection?

Answer 39

all energy of the wave is returned back into the material

Question 40

When does total internal reflection take place?

Answer 40

- light in the material travels towards a material with lower refractive index - angle of incidence is greater than the critical angle

Question 41

When does a critical angle occur?

Answer 41

when the angle of refraction is 90 degrees