P13

Question 1

What are EM waves?

Answer 1

All EM waves are transverse waves that transfer energy from a source to an absorber

Question 2

All EM waves travel at the same …….

Answer 2

Speed through air or a vacuum

Question 3

Why can radio waves be hazardous?

Answer 3

Because they penetrate peoples body’s and can heat the internal parts of the body.

Question 4

Where do radio wave frequency’s range from?

Answer 4

They range from about 300,000Hz to 3000million Hz

Question 5

How can you produce radiowaves?

Answer 5

You can produce radiowaves by using an alternating current in an electrical circuit. The object ( in which charges the electrons and oscillates to create radio waves ) is called a transmitter.

Question 6

What happens when transmitted radio waves reach a reciever?

Answer 6

The radio waves are absorbed and then the energy carried by the waves is transferred to the electrons in the material of the receiver. Then this energy causes the electrons to oscillate.

Question 7

What are radio waves?

Answer 7

Radio waves are EM radiation with wavelengths longer than about 10 cm.

Question 8

Why can long-wave radio waves be transmitted from e.g. London and recieved halfway around the world?

Answer 8

That’s because long wavelengths diffract (bend) around the curved surface of the Earth.

Question 9

Why can short-wave radio signals, like long-wave, be received at long distances from the transmitter?

Answer 9

That’s because they are reflected from the ionosphere - an electrically charged layer in the Earth’s upper atmosphere.

Question 10

What are radiowaves usually used for?

Answer 10

Communication

Question 11

Give an example of a short-wave radio use?

Answer 11

Bluetooth uses short-wave radio to connect devices without cables

Question 12

Communication to and from satellites uses…..

Answer 12

Micro waves

Question 13

How do microwave ovens work?

Answer 13

The microwaves penetrate up to a few centimetres into the food before being absorbed and
transferring the energy they are carrying to the water molecules in the food, causing the water to heat up.

Question 14

How can infrared radiation be used?

Answer 14

It can be used to monitor/increase temperatures

Question 15

Light from ordinary lamps and from the sun is called…

Answer 15

White light

Question 16

The hotter an object is the more …..

Answer 16

Infrared radiation it emits

Question 17

What are fibre optic cables?

Answer 17

Optical fibres are thin glass or plastic fibres that can carry data (e.g. from telephones or computers) over long distances as pulses of visible light.

Question 18

How do fibre optic cables work?

Answer 18

They work because of reflection. The light rays are bounced back and forth until they reach the end of the fibre. ( they bounce on a glass fibre )

Question 19

What is Fluorescence?

Answer 19

Fluorescence is a property of certain chemicals, where ultra-violet (UV) radiation is absorbed and then visible light is emitted.

Question 20

What waves does the sun produce?

Answer 20

Ultraviolet radiation (UV) is produced by the Sun, and exposure to it is what gives people a suntan.

Question 21

Overexposure to UV radiation can be

Answer 21

Dangerous

Question 22

How do X-rays work?

Answer 22

X-rays pass easily through flesh but not so easily through denser material like bones or metal. So it’s the amount of radiation that’s absorbed (or not absorbed) that gives you an X-ray image.

Question 23

Low frequency waves like radio waves don’t transfer much energy so they mostly pass through….

Answer 23

Soft tissue without being absorbed

Question 24

What do UV rays do to your body?

Answer 24

UV radiation damages surface cells, which can lead to sunburn and cause skin to age prematurely.
Some more serious effects are blindness and an increased risk of skin cancer.

Question 25

What can X-rays and gamma rays do to your body?

Answer 25

X-rays and gamma rays are types of ionising radiation. (They carry enough energy to
knock electrons off of atoms.) This can cause gene mutation or cell destruction, and cancer.

Question 26

What is radiation dose a measure of?

Answer 26

Radiation dose (measured in sieverts) is a measure of the risk of harm from the body being exposed to radiation.

Question 27

What does the radiation dose depend on?

Answer 27

-the type of radiation used
-how long the body has been exposed to it
-the energy per second absorbed by the body from the radiation

Question 28

An object that’s hotter than its surroundings….

Answer 28

Emits more IR radiation than it absorbs as it cools down

Question 29

An object that’s cooler than its surroundings….

Answer 29

An object that’s cooler than its surroundings absorbs more IR radiation than it emits as it warms up

Question 30

Objects at a constant temperature….

Answer 30

Objects at a constant temperature emit infrared radiation at the same rate that they are absorbing it.

Question 31

A black surface is better at absorbing and emmiting radiation than a ………

Answer 31

White one

Question 32

White light uses

Answer 32

Photography

Question 33

As you increase frequency in EM waves….

Answer 33

The wavelength decreases