waves

Question 1

what is a transverse wave?

Answer 1

the particles vibrate perpendicular to the direction of wave travel

Question 2

give examples of transverse waves

Answer 2

• ripples on a water surface
• seismic (s) waves
  all electromagnetic waves like…
• micro waves
• light waves
• radio waves

Question 3

what is a longitudinal wave?

Answer 3

the particle vibrations are parallel to the direction of wave travel

Question 4

give examples of longitudinal waves

Answer 4

• sound waves
• ultrasound waves
• seismic (p) waves

Question 5

what is the amplitude of a wave?

Answer 5

distance between the resting position and the maximum displacement of the wave

Question 6

define wavelength

Answer 6

the distance of a point of one length to the equivalent point on the adjacent wave

Question 7

define frequency

Answer 7

the number of waves passing a point each second

Question 8

what is wave speed?

Answer 8

the speed at which energy is transferred (or wave moves) through the medium

Question 9

state the equation for calculating wave speed

Answer 9

wave speed = wavelength x frequency

Question 10

describe a method to measure the speed of sound waves in air

Answer 10

• find a large open space, like a field, and place two people at a known distance apart
• have one person make a loud noise like clapping or whistling
• the second person measures the time it takes for the sound to echo, using a stopwatch
• divide the distance travelled by the time taken to find the speed of sound in air

Question 11

describe a method to measure the speed of ripples on a water surface

Answer 11

• find a calm, still body of water
• place a ruler perpendicular to the direction of the ripple, ensuing that it’s touching the water
• start a stopwatch as soon as a ripple passes the “0” mark on the ruler
• time how long it takes for the ripple to pass a known distance (eg, 20 centimetres)
• repeat the measurement 3 more times to calculate an average time
• use the equation ( distance divided by time) to calculate the speed

Question 12

define transmission

Answer 12

a wave passes across or through a medium

Question 13

define absorption

Answer 13

energy is transferred from the wave, into the particles of a substance

Question 14

give an example of wave energy absorption

Answer 14

• sunlight landing on face, warming skin
• sound waves hitting thick curtains give up their energy, muffling sound
• infrared ration of the sun is absorbed by the surface of the earth

Question 15

give an example of wave energy transmission

Answer 15

• light passing through a glass window continues with over 95% of its energy
• ultrasound waves scanning a baby pass from flesh to bone and continue with enough energy for the machine to detect an echo

Question 16

refraction occurs when…

Answer 16

… a wave changes direction as it passes between the boundary between two mediums

this happens because the wave speed changes as it enters a new medium, causing the wave to bend

Question 17

reflection occurs when…

Answer 17

… a wave hits a boundary between two mediums and does not pass through, but instead stays in the original medium

Question 18

the law of reflection states that:

Answer 18

the angle of incidence = the angle of reflection

Question 19

which surfaces are the most and the least reflective?

Answer 19

MOST
flat, smooth surfaces

LEAST
rough surfaces (light scatters in all directions)

Question 20

if an object appears red, this means that…

Answer 20

• only red light has been reflected
• all other colours have been absorbed

Question 21

describe the effects of sound waves on the eardrum

Answer 21

• sounds waves cause the ear drum to vibrate, causing the sensation of sound
• this conversion of sound waves to solid vibrations works over a limited frequency range

Question 22

state the range of normal human hearing?

Answer 22

20Hz - 20kHz

Question 23

give some uses of ultraviolet

Answer 23

• sterilising (surgical) equipment
• killing microorganisms
• increase growth rate in plants
• water purification
• detecting forged bank notes

Question 24

what property of a light ray changes when it is refracted?

Answer 24

velocity

Question 25

what happens when an ultrasound wave meets a boundary between two different mediums?

Answer 25

it’s partially reflected

Question 26

how are seismic waves produced?

Answer 26

earthquakes

Question 27

describe the properties of seismic-p waves

Answer 27

- longitudinal - can travel through solids, liquids, and gases, but their speed can vary depending on the material - can travel through the earth’s core

Question 28

describe the properties of seismic-s waves

Answer 28

- transverse - cannot travel through liquids, gases, or the earth’s core - slower

Question 29

what is echo-sounding used for?

Answer 29

- detect objects in deep water - measure water depth

Question 30

what are electromagnetic waves?

Answer 30

transverse waves that transfer energy from the source of the wave to an absorber

Question 31

state the electromagnetic wave order, going from the longest to the shortest wavelength

Answer 31

- radiowaves - microwaves - infared - visible light - ultraviolet - xrays - gamma rays (really mad iguanas visit unique xeranthemum gardens)

Question 32

how are radio waves produced?

Answer 32

oscillations in electrical circuits

Question 33

which three waves have hazardous effects on humans?

Answer 33

ultraviolet, x-ray, gamma

Question 34

what is the unit of radiation dose?

Answer 34

sievert

Question 35

what is the danger of using ultraviolet rays?

Answer 35

- can cause skin to age prematurely - increased risk of skin cancer

Question 36

what happens when radio waves are absorbed?

Answer 36

they may create an alternating current with the same frequency as the radio wave itself so…. radio waves can themselves induce oscillations in an electrical current

Question 37

gamma rays origionate from…

Answer 37

… changes in the nucleus of an atom

Question 38

what are the dangers of x-ray and gamma rays?

Answer 38

- mutations in genes and cancer - due to ionising radiation

Question 39

state the practical uses of radio waves

Answer 39

- televisions - radios

Question 40

state the practical uses of microwaves

Answer 40

- satellite communications - cooking food

Question 41

state the practical uses of infared

Answer 41

- infrared cameras - electrical heaters - cooking food

Question 42

state the practical uses of visible light

Answer 42

fibre optic communication

Question 43

state the practical uses of x-ray and gamma rays

Answer 43

medical imaging and treatments

Question 44

how does a lens form an image?

Answer 44

by refracting light

Question 45

state the definition of focal length

Answer 45

the distance from the lens to the principal focus

Question 46

the image produced by a convex lens can be…

Answer 46

real or virtual

Question 47

the image produced by a concave lens is…

Answer 47

always virtual

Question 48

define specular reflection

Answer 48

reflection from a smooth surface in a singular direction

Question 49

define diffuse reflection

Answer 49

reflection from a rough surface, causing light to be scattered

Question 50

an object appears white if…

Answer 50

… all wavelengths are reflected equally

Question 51

an object appears black if…

Answer 51

… all wavelengths are absorbed

Question 52

what is a perfect black body?

Answer 52

- an object that absorbs all of the infrared radiation incident on it - since a good absorber = a good emitter, a perfect black body would be the best possible emitter

Question 53

what does the intensity and wavelength distribution of any emmision depend on?

Answer 53

the temperature of the body

Question 54

a body at constant temperature is…

Answer 54

… absorbing radiation at the same rate that it is emitting it

Question 55

state the factors that determine the temperature of the earth

Answer 55

- rate of absorption and emission of radiation - reflection of radiation into space