Electromagnetic waves

Question 1

electromagnetic spectrum in order

Answer 1

• Radio waves
• Micro waves
• Infra red
• Visible light
• Ultra violet
• X-rays
• Gamma rays

Question 2

Transverse waves

Answer 2

The oscillations are perpendicular to the direction of energy transfer

Question 3

What are EM waves?

Answer 3

Transverse waves that tranfer energy from a source to an absorber

Question 4

How do EM waves travel through air or a vacuum?

Answer 4

At the same speed

Question 5

EM waves wavelengh and frequency are ______ ______?

Answer 5

Inversely related

Question 6

Electromagnetic spectrum as you go left to right

Answer 6

Frequency increases
wavelength decreases

Question 7

Where does EM waves come from?

Answer 7

Everywhere

Question 8

When an EM wave come into contact with something what happens?

Answer 8

• Reflected
• Absorbed
• Transmitted

Question 9

Radio waves properties

Answer 9

-Lowest frequency
-Longest wavelength (+10cm)

Question 10

Why are EM waves called EM

Answer 10

Generated of oscillations (alternating current) of electric and magnetic fields

Question 11

What do we use to generate radio waves

Answer 11

Transmitter Which is usually connected to an oscilloscope

Question 12

Oscilloscope

Answer 12

See the frequency of the alternating current
- determines the frequency of the wave

Question 13

In radio waves, what is the absorber?

Answer 13

The receiver which generates an A.C. and is displayed on another oscilloscope

Question 14

The oscilloscope of the reveiver and the oscilloscope of the transmitter have ____ _____ ______ frequency

Answer 14

The exact same

Question 15

Radio waves uses

Answer 15

Allows us to transfer information (communication)

Question 16

3 Radio waves for communication

Answer 16

• Long waves
• Short waves
• Very short waves

Question 17

Why are long waves used for huge distances?

Answer 17

The waves diffract (bend) around the curved surface of the earth
- wavelength=1-10km

Question 18

How do shortwaves travel long distances?

Answer 18

They are unable to diffract around the earth so they reflect from the ionosphere
- wavelegnth=10m-100m

Question 19

ionosphere

Answer 19

An electrically charged layer in the Earth’s upper atmosphere

Question 20

Very short waves

Answer 20

• TV
• FM radio
  Direct travel

Question 21

Infrared and microwaves properties

Answer 21

-Low frequency
-long wavelengths

Question 22

Microwaves that aren’t absorbed by water molecules, uses

Answer 22

Used for communication using satellites as they can pass easily through the earth’s watery atmosphere

Question 23

How do satellites use microwaves

Answer 23

1. The signal from a transmitter is transmitted
   into space
2. Satellite receiver dish picks up the signal
3. The satellite transmit the signal back to earth
   in a different direction
4. A satellite dish on the ground receives the
   signal
5. slight time delay between the signals being
   sent and received because of the long
   distances.

Question 24

Microwaves that are absorbed by water molecules, uses

Answer 24

Used in microwaves and ovens to heat our food

Question 25

How do ovens use microwaves

Answer 25

Since a lot of our food contain water molecules is absorbs the microwaves waves.
- This gives the water molecules energy making
them vibrate more, transferring some energy
to the neighboring molecules so it spread
throughout the food

Question 26

Infrared radiation

Answer 26

Emitted from all objects that have thermal energy
- The hotter the object the more IR radiation it
gives out

Question 27

Infrared cameras

Answer 27

Detects IR radiation and turns it into electrical signals, which are them displayed onto the screen as a picture
- The hotter the object the brighter it is

Question 28

IR radiation for cooking

Answer 28

Heating metal to very high temp, it can emit lots of IR radiation which can then heat our food by transferring the heat energy.
-Doesn’t penetrate the surface

Question 29

Visible light
What are colours are the longest and shortest wave lengths

Answer 29

• Red is the longest
• Violet is the shortest

Question 30

What can visible light be used for?

Answer 30

Communication through optic fibres

Question 31

What are the advantages of optical fibres?

Answer 31

• Transmit much more info
• Signals is less likely to be distorted

Question 32

Fluorescence

Answer 32

It is a property of certain chemicals where UV radiation is absorbed and then emit visible light

Question 33

Fluorescent lights

Answer 33

1. generates UV radiation
2. This radiation is then absorbed by a layer of
   phosphorus
3. Phosphorus has so much energy so it re-
   emits the energy as visible light

Question 34

Benefits of fluorescent lights

Answer 34

energy efficient
- save energy bills
- save carbon dioxide emissions

Question 35

X-rays and Gamma rays properties

Answer 35

-Short wavelengths
-high frequency

Question 36

How are X-rays used to see the internal view of objects

Answer 36

1. fire x-rays at a person’s body and record the
   waves that get through using a detector plate
2. This works by denser materials, like bones,
   absorb the waves
3. EM waves easily passes through our flesh

Question 37

What are the 2 uses of gamma rays for sterilization

Answer 37

• Food
• Medical equipment

Question 38

Gamma rays

Answer 38

Can kill microorganisms without causing any damage

Question 39

X-rays and Gamma rays in medicine

Answer 39

• Ionising radiation that can kill our cells leading
  to cancer
• Help us to treat/diagnose diseases