chapter 13 - EM waves

Question 1

arrange the types of electromagnetic waves in increasing frequency

Answer 1

radio waves
microwaves
infrared radiation
visible light
ultraviolet radiation
x-rays
gamma rays

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Question 2

state the waves that are red

Answer 2

radio waves
microwaves
infrared radiation

Question 3

what colour is visible light?

Answer 3

all colours - ROYGBIV

Question 4

state the waves that are violet

Answer 4

ultraviolet radiation

Question 5

which wave has the lowest frequency?

Answer 5

radio waves

Question 6

which wave has the shortest wavelength?

Answer 6

gamma rays

Question 7

which wave has the highest frequency?

Answer 7

gamma rays

Question 8

which wave has the longest wavelength?

Answer 8

radio waves

Question 9

state the properties of electromagnetic waves

Answer 9

transverse waves

consist of electric fields and magnetic fields that oscillate 90°/perpendicularly to each other
they do not carry electric charge

can travel without a medium - at 30 x 10^8 in a vacuum

when it travels from one medium to another, its speed and wavelength change ; frequency does not change

they obey the laws of reflection and refraction

they transfer energy from one place to another

ionising waves are those with higher frequencies –> higher energies

Question 10

state how ionising waves be harmful

Answer 10

ionising waves are those with higher frequencies and hence higher energies

they can eject electrons from atoms and molecules to create ions which in turn can cause harm by disrupting cell functions

Question 11

applications of gamma rays

Answer 11

radiotherapy –> to kill cancer cells
example: gamma knife radio surgery

sterilizer –> for sterilisation of medical and laboratory equipment

industry radiography –> for checking of hidden defects

Question 12

health effects of gamma rays

Answer 12

atoms/molecules of living cells are ionised leading to

• cell death/destruction/mutation
• abnormal cell division

which causes

leading to diseases and organ failure

Question 13

applications of x-rays

Answer 13

x-ray imaging/CT scan in medical field –> for medical diagnosis
example: dental inspection, bone fractures

radiotherapy –> energetic X-rays used to kill cancer cells

industrial radiography –> for checking of manufacturing defects in METAL PARTS

x-ray screening –> for screening of baggage and luggage at airports for prohibited items

Question 14

health effects of x-rays

Answer 14

causes cell destruction

causes mutation of normal cells leading to cancer and organ failure

Question 15

application of ultraviolet rays

Answer 15

counterfeit detector machines using UV light –> for the detection of counterfeit money

sunbed –> for artificial tanning

germicidal lamps –> sterilisation of medical and laboratory equipment

Question 16

health effects of ultraviolet rays

Answer 16

causes
- sunburn
- skin cancer
- premature ageing

Question 17

applications of visible light

Answer 17

optical fibre –> endoscopy to illuminate internal organs

optical fibre –> bundled to form thicker undersea cables used to transmit large amount of data

Question 18

health effects of visible light

Answer 18

causes blindness due to direct strong exposure on retina

Question 19

applications of infrared waves

Answer 19

• hotter objects will emit more infrared radiation

intruder alarm system –> to detect the emitted infrared radiation to produce a thermal image

remote controller –> to control electrical devices
example: televisions, air conditioners

electric heaters –> electrically heated rods give out infrared radiation

Question 20

applications of microwaves

Answer 20

*microwaves can penetrate the atmosphere, haze, clouds

microwave ovens –> penetrate into food to cause water molecules to vibrate vigorously, warming the food quickly

wifi signals –> used extensively for communication between devices like mobile phones or computers

satellite telecommunication –> to carry signals to and from satellites for satellite television / GPS (global positioning system) / mobile phone network

Question 21

health effects of microwaves

Answer 21

microwave radiation can heat body tissues the same way it heats food

exposure to high levels of microwaves can cause skin burns or cataract=

Question 22

application of radio waves

Answer 22

*radio waves are not used for satellite telecommunication

AM and FM radios –> for radio and television communication

RFID (radio frequency identification) tag –> used to tag merchandise in warehouses and shops

Question 23

define ionisation

Answer 23

it is a physical process of converting an atom/molecule into an ion by addition or removal of charged particles (eg. electrons)

Question 24

which EM waves are ionising?

Answer 24

gamma rays and x-rays (and higher frequency UV rays)