Ch15 The Electromagnetic Spectrum

Question 1

Define ultraviolet radiation:

Answer 1

Electromagnetic radiation with a shorter wavelength than visible light

Question 2

Define ultraviolet radiation:

Answer 2

Electromagnetic radiation with a shorter wavelength than visible light

Question 3

Define electromagnetic spectrum:

Answer 3

The family of radiations similar to light

Question 4

Define analogue signal:

Answer 4

A signal which varies continuously in frequency and amplitude

Question 5

Define digital signal:

Answer 5

A signal that consists of a series of pulses neither on/of

Question 6

How is an electromagnetic spectrum formed?

Answer 6

When light passes through a prism and some colors are refracted more than others

Question 7

What end of the spectrum is refracted the most?

Answer 7

Violet end

Question 8

What causes different colors light waves?

Answer 8

Different frequencies

Question 9

What physicist described light as small oscillations in electric and magnetic fields which he called electromagnetic waves?

Answer 9

Scottish physicist, James Clerk Maxwell

Question 10

What causes light waves to have different effects on different objects?

Answer 10

The different frequencies of light

Question 11

What is the speed of light in a vacuum?

Answer 11

3 x 10^8 m/s

(Approx. the same speed in air)

Question 12

What has a greater wavelength?
Red light or violet light?

Answer 12

Red light has a greater wavelength

Question 13

What has a bigger frequency?
Red light or violet light

Answer 13

Violet light

Question 14

What is the frequency of visible light?

Answer 14

10^14 Hz

Question 15

What is the wavelength of red light?

Answer 15

700nm (nanometers)

Question 16

What is the wavelength for violet light?

Answer 16

400nm

Question 17

Change 400nm to meters

Answer 17

400 /1 000 000 000 m

Question 18

List the names of the waves in the electromagnetic spectrum in order of increasing wavelength:

Answer 18

1) Gamma rays
2) X-rays
3) Ultraviolet
4) Visible light
5) Infrared
6) Microwaves
7) Radiowaves

Question 19

List the names of the waves in the electromagnetic spectrum in order of increasing frequency:

Answer 19

1) Radio waves
2) Microwaves
3) Infrared
4) Visible light
5) Ultraviolet
6) X-rays
7) Gamma rays

Question 20

Name 2 uses of radio waves:

Answer 20

1) broadcast radio/television
2) RFID chips with medical information/passport/contactless bank card

Question 21

What does RFID stand for?

Answer 21

Radio frequency identification

Question 22

Give 2 uses for microwaves:

Answer 22

1) Satellite television broadcasting
2) Transmit mobile phone signals between masts
3) microwaves ovens emit microwaves which are absorbed by molecules in food causing heat

Question 23

Give uses for 5 uses for infrared radiation:

Answer 23

1) remote controls for devices (such as tv remote)
2) grills and toasters use IF radiation to cook food
3) also used together with optical fibers
4) can be used in medicine to detect heat which may indicate infection
5) can be used in medicine to speed up healing and reduce pain

Question 24

Give 2 uses for visible light:

Answer 24

1) photosynthesis
2) provides us with vital information about the world through our eyes, cameras, telescopes

Question 25

Give **3** uses for **ultraviolet light**:

Answer 25

*Causes some chemicals (sweat, saliva) to emit visible light. 1) forensic scientists use this to **find evidence** at crime scenes invisible to the human eye 2) chemicals that glow under UV can be used for **security marking** such as bank notes /valuable equipment 3) **sterilize water** (UV kills DNA in bacteria/viruses contained in water which makes them useless)

Question 26

Give uses for **X-rays**:

Answer 26

*Can penetrate solid material 1) used in **security scanners** in airports 2) used in hospitals and clinics to **see inside patients** without the need for surgery

Question 27

How do x-rays work?

Answer 27

Some material absorbs x-rays more than other causing them to create a darker shadow on the scan

Question 28

Give uses for **gamma rays**:

Answer 28

1) **damage/kill living cells** Targeted beam of gamma rays can be used to **kill cancerous cells** 3) **sterilize** surgical instruments by killing bacteria 4) can detect cancer

Question 29

Why can **infrared radiation** be *hazardous*?

Answer 29

Can burn you

Question 30

Why can **UV radiation** be *hazardous*?

Answer 30

Can damage skin cells which may leas to skin cancer Can damage eye cells - wear sunglasses/ hat in bright light

Question 31

True/false: The **heigher the frequency** of the wave, the **greater harm** it can cause

Answer 31

True

Question 32

What 2 rays are the most dangerous part of the electromagnetic spectrum and **why**?

Answer 32

1) X-rays 2) Gamma rays Can cause **cell mutations** that might lead to cancer

Question 33

How can workers protect themselves from the dangerous radiation when working with gamma/X-rays?

Answer 33

1) Stand well away when a patient is being examined 2) Enclose the equipment in a metal case to absorb the rays

Question 34

Compare **geostationary satellites** and **low earth orbit satellites**?

Answer 34

**Geo** **1)** *Orbit at the same rate as what earth turns* so they stay above one point of the earths surface **2)** *35 000km* above the earths surface and above the equator **3)** Waves travel a long way to satellite - *delay* in conversation **4)** covers a large area **5)** transmits data fast - suitable for satellite tv and some phones **Low earth** **1)** Orbit earth in *2 hours * **2)** *2000km* above earths surface **3)** Waves don’t have travel that far - *no delay* in conversation **4)** more needed as they only cover a *small* area of earths surface **5)** does not transmit data fast - not suitable for tv transmissions

Question 35

Why are **microwaves** most suitable for mobile phones and wireless internet?

Answer 35

1) can pass through most walls 2) only need a small aerial

Question 36

What radiation is used for Bluetooth?

Answer 36

Radio waves *connection is weakened as passes through walls *short range signal is useful for communication between electronic devices such as in hands-free mobile phone systems

Question 37

What radiation does **optical fibers** use and *why*?

Answer 37

Infrared radiation Visible light *Optical fibers are made of glass and transparent to IR and visible light *These waves have higher frequency and carry more data *This is vital for high speed broadband connections

Question 38

Give an example of an analogue signal:

Answer 38

Sound wave

Question 39

Compare analogue and digital signal:

Answer 39

**Analogue** **1)** electrical signal transmitted through copper wires **2)** transmission process for analogue signals cause wave to become distorted and unwanted vibrations are heard as noise **3)** slower since sound wave is converted to electrical signal and then back to sound wave **4)** varies continuously **Digital** **1)** electrical signal transmitted through optical fibers **2)** clearer **3)** faster and carry more data **4)** either on/off

Question 40

Describe what happens with radiation during making a digital phone call:

Answer 40

1) analogue sound wave from caller is **encoded by converter** 2) converter turns sound wave into **series of pulses** 3) digital signal is **carried along optical fibers** by visible pulses/infrared waves 4) signal **passes through** 1/more **regenerators** that clean up signal **removing any distortion** 5) regenerators **boost** the signal if it has lost power 6) **second converter** switches the signal back to an **analogue signal** which can be **converted** back to **sound wave**

Question 41

Why is visible light referred to as electromagnetic radiation?

Answer 41

It is because there are electric and magnetic fields that make up the radiation

Question 42

Are electromagnetic waves, transverse, or longitudinal?

Answer 42

Transverse

Question 43

What are the **two components** of an electromagnetic wave?

Answer 43

**Electric field** oscillating in one plane produces a **magnetic field** oscillating in a plane at **right angles** to it, oscillating at the same frequency

Question 44

What causes the electromagnetic wave to propagate forward?

Answer 44

When two oscillating electric and magnetic fields regenerate each other (mutually regenerating) It causes the wave to propagate forward.

Question 45

What does the symbol **c** stand for?

Answer 45

Speed of electromagnetic wave through space 3 x 10^8 m.s^-1

Question 46

What’s a logarithmic scale?

Answer 46

A method for graphing and analyzing a broad range of values in a compact form

Question 47

Frequency and wavelength is inversely proportional Give a statement to prove this:

Answer 47

As frequency of a wave increases, wavelength decreases. This allows speed to stay constant for all electromagnetic waves.

Question 48

What are all electromagnetic waves produced by?

Answer 48

Produced by accelerating charged particles, especially electrons

Question 49

What is the formula that involves, **speed of light**, **frequency** and **wavelength**?

Answer 49

c = f x λ *c is speed of light, 3 x 10^8 m.s^-1 *f is frequency, Hertz (Hz) *λ wavelength, meters (m)

Question 50

What is ionisation?

Answer 50

The process of breaking an electron away from an atom

Question 51

What is non-ionizing radiation?

Answer 51

Radiation that does not have enough energy to break an electron way from an atom

Question 52

Why is ionizing radiation dangerous?

Answer 52

Ionizing radiation has enough energy to break an electron away from an atom. This means ionizing radiation has the ability to change the chemical composition of the material it comes into contact with (causes mutations in DNA molecules)

Question 53

What are **the only 2** types of electromagnetic radiation that is **ionising**?

Answer 53

Gamma rays X-rays