ch12 - waves

Question 1

waves

Answer 1

a periodic disturbance travelling through space, characterised by a vibrating medium

Question 2

progressive waves

Answer 2

a wave that carries energy from one place to another, all waves are progressive

Question 3

displacement (waves)

Answer 3

the distance of a point on the wave from its undisturbed / equilibrium position, vector, distance travelled in a particular direction

Question 4

wavelength

Answer 4

the distance between two adjacent points on a wave oscillating in step with each other, m

Question 5

period, T

Answer 5

the period of an oscillating system or point in a wave is the time taken to make one complete oscillation, s

Question 6

frequency

Answer 6

the number of oscillations per unit time of a point in a wave, Hz

Question 7

f = 1 / T

Question 8

mechanical waves

Answer 8

need a substance to travel through

Question 9

longitudinal waves

Answer 9

a wave in which the particles of the medium oscillate along the direction in which the wave travel

Question 10

transverse waves

Answer 10

a wave in which the particles of the medium oscillate at right angles to the direction in which the wave travels

Question 11

difference between longitudinal and transverse

Answer 11

longitudinal - parallel (sound)
transverse - perpendicular (electromagnetic)

Question 12

compressions

Answer 12

the point in a sound wave at which the air pressure is at maximum

Question 13

rarefactions

Answer 13

a region in a sound wave where the air pressure is less than its mean value

Question 14

phase difference

Answer 14

the difference in the phases of two oscillating particles measured in degrees or radians

Question 15

particles oscillating in step have a phase difference of:

Answer 15

0, 2pi etc

Question 16

particles oscillating in antiphase have a phase difference of:

Answer 16

pi, 3pi etc
180, 270 etc

Question 17

phase difference formula

Answer 17

circle with line through =
x/wavelength * 360

Question 18

intensity

Answer 18

the rate of energy transmitted per unit area at right angles to the wave velocity

Question 19

intensity formulas

Answer 19

intensity = power / area
I prop. to A² (amplitude)

Question 20

wave speed

Answer 20

speed with which a wave is transmitted, ms-1

Question 21

v = f¥ (wavelength)

Question 22

speed, frequency and wavelength of water waves

Question 23

speed, frequency and wavelength of water waves

Answer 23

speed = 0.12
frequency = 6
wavelength = 0.2

Question 24

speed, frequency and wavelength of sound waves in air

Answer 24

speed = 330
frequency = 20 to 20000
wavelength =16.5 to 0.0165

Question 25

doppler effect

Answer 25

the change in frequency or wavelength of a wave observed when the source of the wave is moving towards or away from the observer

Question 26

doppler effect formula

Answer 26

v = speed of waves
Vs = speed of source
¥o = observed wavelength
fo = observed frequency

fo = fs * v / (v±vs)

Question 27

electromagnetic spectrum

Answer 27

the family of waves that travel through a vaccum at a speed of 3 * 10^8 ms-1

Question 28

magnetic field

Answer 28

a force field in which a magnet, a wire carrying a current, or a moving charge experiences a force

Question 29

electromagnetic wave

Answer 29

a transverse wave travelling through space as vibrations of electric and magnetic fields

Question 30

radio waves discovered by

Answer 30

Heinrich Hertz

Question 31

x rays discovered by

Answer 31

Wilhelm Röntgen

Question 32

gamma rays discovered by

Answer 32

Henri Becquerel

Question 33

speed of light

Answer 33

c = 3 * 10^8 ms-1

Question 34

c = f¥

Question 35

wave speed (v) = c

Question 36

wavelength visible to human eyes

Answer 36

400nm to 700nm

Question 37

wavelength range of radio waves

Answer 37

> 10^6 to 10^-1

Question 38

wavelength range of microwaves

Answer 38

10^-1 to 10^-3

Question 39

wavelength range of infrared waves

Answer 39

10^-3 to 7*10^-7

Question 40

wavelength range of visible light

Answer 40

7 × 10^-7 to 4 × 10^-7

Question 41

wavelength range of ultraviolet

Answer 41

4 * 10^-7 to 10^-8

Question 42

wavelength range of x rays

Answer 42

10^- 8 to 10^- 13

Question 43

wavelength range of gamma rays

Answer 43

10^-10 to 10^-16

Question 44

electric field

Answer 44

a force field or region in which an electric charged particle or object experiences a force

Question 45

electric and magnetic field are

Answer 45

perpendicular

Question 46

plane polarised

Answer 46

decribes a transverse wave with oscillation in just one plane

Question 47

which waves can be polarised

Answer 47

TRANSVERSE

Question 48

what wave can make a unpolarised wave be plane polarised

Answer 48

a vertical slit

Question 49

what can be used to polarise sunlight

Answer 49

transparent polymer material, eg Polaroid

Question 50

why use a polariod to polarise light

Answer 50

. has long chains of molecules in one direction
. electric field vibrations along these chains are absorbed
. energy absorbed become thermal
. electric field vibrations at right angles to molecule chains are transmktted with negligible absorption

Question 51

two polariods in the same direction

Answer 51

plane polarised light transmitted

Question 52

two polaroids in different directions (90°)

Answer 52

no light transmitted

Question 53

Malu’s law

Answer 53

I = Io cos²x