Waves

Question 1

Waves

Answer 1

Transfer of energy through a medium caused by oscillation or vibration
-energy is tranferred not matter

Question 2

Longitudinal waves

Answer 2

• medium oscillates parallel to the direction of energy travel
• caused by compressions and rarefactions of same medium
• cant travel in vacuum as particals are needed so change of density
• eg. Sound, mechanical waves (slinky/spring), deep water waves, earthquakes, AC

Question 3

Transverse waves

Answer 3

• field oscillates perpendicular to direction of energy transfer
• caused by vibrations of field/medium
• density is constant
• can travel through medium
• light, em waves,ripples on water

Question 4

Human ear range- sound waves

Answer 4

20HZ-KHz

Question 5

What is amplitude in sound measured in

Answer 5

Decibels

Question 6

Ultrasound

Answer 6

• frequency above 20khz

- used in sonograms(pregnany scans), echolocation, cleaning

Question 7

Infrasound

Answer 7

-sound below 20Hz

Question 8

Dangers of sound

Answer 8

• xtremely loud sounds- extreme pressure changes- force on eardrum bsting it
• exposure to loud sounds over long time- damage

Question 9

How to prevent danger of sounds

Answer 9

• ear protection
• shorter time w/ loud sounds
• positioning behind sound

Question 10

Refraction

Answer 10

Wave changes direction due to change in soeed at boundry

-depends on refractive index

Question 11

Plano

Answer 11

Flat one side

Question 12

Double

Answer 12

Both sides

Question 13

Convex

Answer 13

Wider middle

Question 14

Concave

Answer 14

Smaller in middle

Question 15

Focal point

Answer 15

Point at which parallel light rays (which have passed through a lens) converge

• determined by shape and material of len
• sharp images formed at focal point

Question 16

Converging rays

Answer 16

-light rays focus on one point

Question 17

Diverging rays

Answer 17

-spread out as if from one point

Question 18

Frequency

Answer 18

How many waves pass a point per second

Question 19

Time period

Answer 19

How ong it takes for one complete osciallation or cycle

Question 20

Wavelength

Answer 20

Distance two neighboring peaks

Question 21

Amplitude

Answer 21

-maximum displacement of the vibration from rest

Question 22

High pitch

Answer 22

• higher frequency

- same heught amplitude

Question 23

Higher volume

Answer 23

Higher amplitude

Same wavelength and frequency

Question 24

As wave speed increases

Answer 24

Bends away from normal

Question 25

What happens when a wave is absorbed

Answer 25

- wave stops travelling - goes into but not through medium - energy is transferred to the material, causing the material’s energy store to increase - kinetic store- moves - internal energy stores-heat up or change state - chemical energy store- light waves photosynthesis

Question 26

Wave is transmitted

Answer 26

Wave continues moving through medium - wave may be changed- diffraction and rfraction - eg. Light through glass, sound through air

Question 27

Diffaction

Answer 27

- waves spread out when passes through gap or round corner - narrower the gap/greater the wavelength- more the diffraction - only occurs if the gapsize is approx same as wavelength - wavelength, frequency and speed unchanged

Question 28

TIR

Answer 28

Total internal reflection - greater than critical angle- light reflects beack into medium - light must be traveling from a more optically dense medium into less optically dense medium (glass to air)

Question 29

At critical angle

Answer 29

- emergent ray is perpendicular to normal | - moves along boundry

Question 30

Optical fibres

Answer 30

- long thin rod of glass - uses tir to transfer info by llight - used medicine-endoscopy - communications- high speed data transfer

Question 31

Positives of optical fibres

Answer 31

- high bandwidth-lots info per second - cheaper than copper - long distances without losses

Question 32

Negatives optical fibres

Answer 32

- complex | - more fragile

Question 33

Telecoms- optical fibres

Answer 33

- info sent at speed of light through binary code (turning light on and off) - interpreted by computer

Question 34

Endoscopy- optical fibres

Answer 34

- doctors use so can diagnose or surgery - light shone one end- tir - light reflects back into another fibre- taking info up to camera so doctor can see

Question 35

Dispertion

Answer 35

- seperating of diff wavelengths (colours) of white light upon reraction through a glass prism - roygbiv from top (red at top, violet at bottom)

Question 36

Greater wavelength

Answer 36

- slower the speed | - greater refractive index