Ch12 Wave properties

Question 1

Electromagnetic wave properties

Answer 1

All travel through a vacuum at 3x10^6 km/s

Question 2

Transverse waves

Answer 2

The oscillations are perpendicular to the direction in which the waves transfer energy

Question 3

Longitudinal waves

Answer 3

Oscillations of a longitudinal wave are parallel to the direction in which the waves transfer energy

Question 4

Examples of transverse waves

Answer 4

1. Waves on a rope
2. Ripples in water
3. Electromagnetic waves
4. S-waves

Question 5

Examples of longitudinal waves

Answer 5

1. sound waves

2. P-waves

Question 6

Wave speed

Answer 6

v = frequency x wavelength

Question 7

Frequency equation

Answer 7

1/ period(T)

Question 8

Amplitude of a wave

Answer 8

Maximum displacement of a point on a wave from its in disturbed position

Question 9

Frequency

Answer 9

The amount of waves passing a fixed point per second

Question 10

Period

Answer 10

The amount of time taken for each wave to pass a fixed point

Question 11

Period equation

Answer 11

period = 1/ frequency

Question 12

Speed of sound in air

Answer 12

340m/s at 15degrees

Question 13

Ears range frequency

Answer 13

20Hz - 20KHz

Question 14

Ultrasound waves

Answer 14

Sound wave that vibrates above 20KHZ

Non-ionising

Question 15

How ultrasound machine works

Answer 15

1. Transducer transmits and detects sets of ultrasound waves
2. Waves are partially reflected back to device at boundaries between different types of mediums(tissues)
3. If you know the speed of the wave and how long it takes to be reflected, can work out how far away boundary is (s = 1/2t x v)
4. Scans internal structure(e.g organs) and is used to build up image of internal tissue

Question 16

Uses of ultrasound

Answer 16

1. medical imaging( e.g. prenatal scans)
2. industrial imaging (e.g crack in supposed solid structure)
3. echo sounding(e.g. sea floor)

Question 17

Seismic waves

Answer 17

Produces by earthquakes

Question 18

Primary waves

Answer 18

last about 1 minute

Push and pull on Earth’s material

Question 19

Secondary waves

Answer 19

Slower than primary waves

Shake material that they pass through from side-side

Question 20

L-waves

Answer 20

slowest
violent movement up-down and forwards-back
only occur in the crust

Question 21

Shadow zone(liquid outer-core under the mantle)

Answer 21

1. P-waves are refracted at boundary between mantle and outer core because speed changes abruptly at boundary
2. S-waves can’t travel through liquid outer core because they are transverse

Question 22

Boundary between crust and mantle

Answer 22

Discovered when found out speed of seismic wave changed at depth of 50km below surface

Question 23

Core has solid inner part

Answer 23

Weak P-waves detected in shadow zone

Solid inner part refracts P-waves at boundary between outer core and inner core into the shadow zone