Physics unit 1 (booklet 2) flashcards

TOTAL INTERNAL REFLECTION

What is total internal reflection?

When the angle of incidence is greater than the critical angle, causing light to be reflected inside the medium

TOTAL INTERNAL REFLECTION

What happens when light travels from glass (optically dense) to air (less dense)?

it bends away from the normal

TOTAL INTERNAL REFLECTION

When is the angle of refraction greater than the angle of incidence?

When light moves from a dense medium to a less dense medium

TOTAL INTERNAL REFLECTION

What is the critical angle?

The angle of incidence that gives a 90 degrees refracted ray

TOTAL INTERNAL REFLECTION

1. What happens when a wave enters a denser medium at an angle to the normal?

2. What happens when a wave enters a less denser medium at an angle to the normal?

1. It bends towards the normal because the waves slow down

2. It bends away from the normal because the waves speed up

COMPARE OPTICAL FIBRES AND TRANSMISSION/SATELLITES ( SPEED, RELIABILITY AND SECURITY)

SPEED:

Optical fibre- uses light so it is much faster and has high bandwidth

Transmission- slower than fibre, limited bandwidth

RELIABILITY:

Optical fibre- not affected by weather, no electrical interference and very reliable

Transmission- affected by weather, less reliable and can suffer signal interference

SECURITY:

Optical fibres- very secure as they cannot be easily tapped into

Transmission- less secure as signals can be intercepted more easily

SIMILARITIES:

• Both used for communication

• Both can transmit large amounts of data

• Both require specialised equipment

• Both carry high frequency signals

COMPARE SINGLE MODE FIBRE TO MULTI MODE FIBRE

• Single mode is very narrow and multi mode is wider

• Single mode allows one mode for light to travel through its core, multi mode allows multiple modes of light to travel at same time

• Single modes have a higher bandwidth and multi modes have more dispersion which reduces performance over long distances

SIMILARITIES:

• Both transmit light signals for data transfer

• Both rely on total internal reflection to guide light

• Both are used in telecommunications, data networks

ANALOGUE AND DIGITAL SIGNALS

What is an analogue signal?

A signal that varies smoothly and continuously

ANALOGUE AND DIGITAL SIGNALS

What is a digital signal?

A signal made of discrete steps, usually 0s and 1s 

ANALOGUE AND DIGITAL SIGNALS

1. What does sampling mean?

2. What happens if a signal is sampled too slowly?

1. Measuring the value of a signal at regular intervals 

2. The digital version become inaccurate

ADVANTAGES AND DISADVANTAGES OF DIGITAL SIGNALS

• Better signals over long distances as data can be regenerated (adv)

• Less affected by noise- Signal quality remains consistent even over long distances (adv)

• Higher reliability because the signal is represented as discrete binary values (adv)

Disadvantages:

• More bandwidth is often required for transmission compared to analogue.

• Digital devices can be expensive to design and maintain.

ADVANTAGES AND DISADVANTAGES OF ANALOGUE SIGNALS

Advantages:

• Natural and continuous representation of real-world data (e.g., sound waves).

• Simple equipment can process analogue signals.

Disadvantages:

• Less reliable because small changes in signal can affect the output.

• Difficult to store and reproduce accurately because quality degrades over time.

Give a reason for using a higher sampling rate when converting from an analogue to digital signal

Signal is more accurate and better quality

Explain why digital signals are regenerated at regular intervals

Reduces noise to improve quality

ELECTROMAGNETIC SPECTRUM

What do all electromagnetic waves have in common?

They all travel at the speed of light

ELECTROMAGNETIC SPECTRUM

The higher the frequency of the wave, the?

The more information per second it can carry

MICROWAVES

1. Why are microwaves useful for satellite communication?

2. Why do satellite dishes have curved reflectors?

1. they can penetrate the atmosphere

2. To focus waves onto the reciever

MICROWAVES

1. Why are microwaves used for mobile phone networks?

2. What is the reception/quality of the signal affected by?

1. Because their high frequency gives greater bandwidth which allow many different frequency bands to transmit large amount of data

2. Wet weather as microwaves are strongly absorbed by water

RADIO WAVES

What is the difference between long wave and short wave radio?

Long waves cannot get high up in the ionosphere so it is limited to line of sight communication.

Short waves have higher frequency and can pass high up into the ionosphere

SATELLITES

1. Where do satellites orbit?

2. Why can satellites send signals over long distances?

3. What types of waves do satellites use to send and receive signals?

1. Above the earths atmosphere

2. There is virtually no absorption of microwaves in space

3. Microwaves

SATELLITES

1. Why are upload and download frequencies different for satellites?

2. Can signals be passed between satellites?

1. To avoid interference between signals

2. Yes- some signals are relayed through multiple satellites to reach their destination 

MOBILE PHONES

Why can mobile phones only use microwaves for short distances?

Microwaves cannot travel long distances near ground level without loss or obstruction

MOBILE PHONES

How do mobile phones use microwaves to transmit information to another phone?

• MW carries signal over a short distance to the nearest base station

• The base station sends the signal through a fibre optic cable

• The central office sends signal & sends it back out along fibre optic cable cable to base station nearest the receiver.

• The base station uses MW again to transmit the signal to receiver’s phone

BLUETOOTH VS WIFI

COMPARE BLUETOOTH AND WIFI

        Differences:

• Bluetooth has lower speeds, wifi has higher speeds

• Bluetooth has low power, wifi has high power

• Bluetooth has a lower bandwidth, wifi has higher bandwidth

• Bluetooth has a short range, wifi has medium range

Similarities:

• Both have wireless communication

• Both operate using radio waves

• Both support data transfer

BLUETOOTH AND WIFI

1. Why does bluetooth use a system of frequency hopping?

2. Can Wi-Fi pass through walls?

1. to reduce interference with Wi-Fi as this uses similar frequencies, this limits data loss

2. Yes- it allows signals to be received in different rooms in a house

Explain why the glass fibre is surrounded by glass cladding

• cladding increases critical angle

• Allows TIR keeping light trapped inside fibre

• Fewer reflections