P13 - Electromagnetic Waves

Question 1

What is ionisiation?

Answer 1

The process by which atoms become charged

Question 2

What is a radiation dose?

Answer 2

Amount of ionising radiation that a person receives

Question 3

What is wave speed?

Answer 3

The distance travelled per second by a wave crest or trough

Question 4

What is white light?

Answer 4

Light that includes all colours of the spectrum

Question 5

What is the structure of an electromagnetic wave?

Answer 5

Electromagnetic waves are transverse waves that transfer energy. The vibrations come in the form of electric and magnetic fields that make up the EM wave. They oscillate 90* to the direction in which the wave is travelling (The electric field also oscillates 90* to the magnetic field).

Question 6

What is are the properties of an electromagnetic wave?

Answer 6

• They are transverse waves.
• They can travel through a vacuum (they do not require a medium to travel through).
• They travel at the speed of light
• EM waves with a high frequency have high energy, while low frequency waves have low energy
• They form a continuous spectrum

Question 7

What is an electromagnetic wave?

Answer 7

Electrical and magnetic disturbances that transfer energy from one place to another

Question 8

What is the order of the EM spectrum (from long wavelength to short) (low frequency to high)

Answer 8

Radio Waves
Microwaves
Infrared
Visible Light
Ultraviolet Light
X-rays
Gamma radiation

Question 9

What is the speed of light in a vacuum?

Answer 9

3.0x10^8

Question 10

What is the equation for the speed of a wave?

Answer 10

Wave speed = Frequency x wavelength

Question 11

What are the properties of a short wavelength carrier wave?

Answer 11

• More information carried
• More energy carried
• Shorter range (greater absorption by the atmosphere)
• The less they spread out

Question 12

What are the properties of a long wavelength carrier wave?

Answer 12

• Less information carried
• Less energy carried
• Greater range (less absorption by the atmosphere)
• The more they spread out

Question 13

What are the 3 types of ionising EM radiation?

Answer 13

• UV Light (higher energy UV rays ONLY)
• X-rays
• Gamma radiation

Question 14

How are gamma rays produced?

Answer 14

Gamma rays are produced when unstable nuclei in radioactive substances decay and release energy in the form of EM waves

Question 15

Describe the penetrating power of Gamma rays and X-rays

Answer 15

Gamma rays and X-rays both are highly penetrating as they have short-wavelengths (therefore carry much more energy than longer wavelength EM waves). Gamma rays have shorter wavelengths than X-rays and are therefore more strongly penetrating

Question 16

What are the dangers of X-rays and Gamma radiation, and how do you protect against them?

Answer 16

They are highly penetrative and are also forms of ionising radiation. This means they may cause mutations in cells which may lead to a cancerous tumour forming. To protect against them you should wear a thick plate of lead

Question 17

Describe how ionising radiation works?

Answer 17

High-frequency radiation (UV, X-ray, Gamma) can knock electrons out of a substance as it passes through. This process is known as ionisation. If it happens to the atoms of living cells it can damage the cell, causing mutation of genes and cancerous growth. At higher doses it can kill the cell

Question 18

What are 2 advantages of using an X-ray?

Answer 18

• They can accurately show if bones are broken or teeth contain cavities
• They can be used to destroy cancerous tumours

Question 19

What are 2 disadvantage of using X-rays?

Answer 19

• They are a form of ionising radiation, in high doses they may cause cancer
• They cannot distinguish between soft tissue

Question 20

Why can Ultrasound waves be used to image organs and unborn babies?

Answer 20

Ultrasound waves are used to image unborn babies and organs inside the human body. This is because ultrasound waves are partially reflected at body organs. This is because body organs have a different density to surrounding tissue. This means some of the ultrasound waves are reflected and detected by the transducer and used to form an image.

Question 21

Describe one use of ultrasound for medical treatment (not medical imaging)

Answer 21

destruction of kidney stones

Question 22

What do waves not transfer?

Answer 22

Matter

Question 23

What is an alternating current?

Answer 23

a current that repeatedly reverses its direction

Question 24

Why are X-rays used to detect internal cracks in metal objects

Answer 24

The more dense an object is, the more X-rays it absorbs from an X-ray beam passing through it. This different amounts of X-rays received on the opposite side of the metal object can be used to detect if there is a crack inside the metal object

Question 25

What is a film badge and what does it do?

Answer 25

A device containing photographic film which registers the wearer’s exposure to radiation. This allows the users exposure to radiation to be monitored

Question 26

How can gamma radiation be used in sterilisation?

Answer 26

Gamma rays are extremely high energy. Exposing food to gamma rays kills 99% of disease-carrying bacteria and pathogens. They can also be used to sterilise and kill any harmful bacteria on medical instruments

Question 27

How can organs made from soft tissue be imaged using an X-ray?

Answer 27

The organ can be filled with a substance called a contrast medium that absorbs X-rays. This enables the interanl surfaces in the organ to be seen on the radiograph.

Question 28

What does a radiation dose depend on?

Answer 28

• The type of radiation used
• How long the body is exposed to the radiation
• The energy per second absorbed by the body from the radiation