Electromagnetic waves and sound waves

Question 1

transverse wave

Answer 1

vibrations are perpendicular to the direction of wave motion

Question 2

longitudinal waves

Answer 2

vibrations are parallel to the direction of wave motion

Question 3

waves

Answer 3

transfer of energy by vibrations without a medium

Question 4

examples of transverse waves

Answer 4

electromagnetic spectrum, water waves, seismic S-waves, light waves

Question 5

examples of longitudinal waves

Answer 5

sound waves, seismic P-waves

Question 6

echo

Answer 6

the reflection of sound waves

Question 7

wave speed formula

Answer 7

speed = frequency x wave length

Question 8

electromagnetic waves

Answer 8

Radio waves, microwaves, infrared waves, visible light, ultraviolet, xrays, gamma rays

Question 9

largest wavelength, lowest frequency (EM)

Answer 9

Radiowaves

Question 10

smallest wavelenth, largest frequency (EM)

Answer 10

Gamma rays (y)

Question 11

speed of EM waves in vacuum

Answer 11

3.0 x 10^8m/s

Question 12

Use of radio waves

Answer 12

communication and broadcasting (TV and Radio)

Question 13

Use of microwaves

Answer 13

Heating food, communication (moblie phones, wifi, satellites)

Question 14

How do microwaves work (in terms of satellite communication)?

Answer 14

Their shorter wave length means they can penetrate the atmosphere and reach the orbiting satellites. Then, the wave will be reflected to where needed.

Question 15

How do radiowaves work (in terms of communication)

Answer 15

They reflect off the ionsphere and to a place in the line of sight

Question 16

How do microwaves heat food?

Answer 16

The waves cause the water molecules to vibrate, producing heat energy to cook food.

Question 17

Infrared uses

Answer 17

electrical heaters and conventional ovens/grills, heat detectors, tv remotes, thermal imaging and intruder alarms

Question 18

Visible light uses

Answer 18

photography, sight, optic fibres

Question 19

How does visible light make optic fibres possible?

Answer 19

Visible light can go through total internal reflection, making it reflect back into the fibre continuously

Question 20

Ultraviolet uses

Answer 20

energy efficient light bulbs, suntanning, curing inks and resin, sterilisation, fake bank note checking,

Question 21

How does ultraviolet waves make energy efficient light bulbs - fluorescent light bulbs?

Answer 21

An electric current excites the gas, moving its atoms to a higher energy level. When they ‘de-excite’ - they emit UV waves. These are absorbed by the coating on the bulb and emit fluorescence.

Question 22

Xray uses

Answer 22

medical imaging, airport secruity, and industry

Question 23

How do xrays allow medical imaging?

Answer 23

X-rays are able to penetrate soft tissue but are absorbed by bones. A photographic plate is blackened where it receives X-rays, and the bones leave a white “shadow”.

Question 24

Gamma ray uses

Answer 24

sterilisation of medical tools and food, treating cancer

Question 25

What do bluetooth devices use?

Answer 25

Low energy radio waves or microwaves, they can pass through walls but the signal is weakened doing so.

Question 26

What do mobile phones use?

Answer 26

microwaves, because they can penetrate some walls and only require a short aerial for transmission and reception

Question 27

What waves do optical fibres use?

Answer 27

Visible light and infrared. Visible light and short wavelength infrared can carry high rates of data.

Question 28

speed of sound in air

Answer 28

330 - 350 m/s

Question 29

relative speed of sound in gases, liquids and solids

Answer 29

Fastest in solids, then liquids and slowest in gases. Because particles are closer to eachother in solids.

Question 30

How does increased temperature effect speed of sound?

Answer 30

Increased temperature increases speed of sound as particles have higher kinetic energy and so there is a higher rate of collisions, easier energy transfer

Question 31

difference between digital and analogue signal

Answer 31

Analogues signal changes in frequency and amplitude all the time in a way that matches the changes in the voice or music being transmitted. Digital signals have only two values - 0 and 1.

Question 32

two ways sound can be transmitted

Answer 32

as a digital or analogue signal

Question 33

benefits of digital signaling

Answer 33

increased rate and range of transmission due to accurate signal regeneration

Question 34

What waves are used for communication with artificial satellites

Answer 34

microwaves: a) some satellite phones use low orbit artificial satelites b) some satellite phones and direct broadcast satellite television use geostationary satellites

Question 35

what do some satellite phones use?

Answer 35

low orbit artificial satellites

Question 36

what do some satellite phones and direct broadcast satellite television use?

Answer 36

geostationary satellites

Question 37

geostationary satellite

Answer 37

a satellite that appears to be located at a fixed point in space when viewed from the earth's surface

Question 38

how is sound produced?

Answer 38

to produce sound an object needs to be vibrating and pushing on the air around it to generate the longitudinal wave that is transmitted through the air (or water)

Question 39

compression

Answer 39

region in which the particles of the wave are closest to each other

Question 40

rarefraction

Answer 40

region in which the particles of the wave are far from eachother.

Question 41

increase in amplitude increases...

Answer 41

volume

Question 42

increase in frequency increases..

Answer 42

pitch

Question 43

ultrasound

Answer 43

a sound with a frequency higher than 20 kHz

Question 44

uses of ultrasound (non-destructive)

Answer 44

testing of materials, medical scanning of soft tissue and sonar

Question 45

how does medical scanning with ultrasound work?

Answer 45

A small transducer (probe) transmits sound waves into the body and records the waves that echos back. Sound waves travel into the area being examined until they hit a boundary between tissues. At these boundaries some of the sound waves are reflected back to the probe, while others travel further until they reach another boundary and are reflected back. Since the speed, direction, and distance sound waves travel differ depending on the boundary they run into, a computer can interpret this information as a two-dimensional image on a screen. (DONT NEED THIS MUCH DETAIL)

Question 46

how does ultrasound work in terms of testing materials?

Answer 46

a probe/transducer sends sound waves through the material they want to test. if there are no defects, the sound waves will pass through, but if the sound waves hit a defect they will bounce of it, indicating its prescence