Section 3 Flashcards
What does diffracted mean?
Bend round edges and through gaps, causing the waves to spread out.
When do waves diffract?
When they pass through a gap or past the edge of an object.
What does the amount of diffraction depend on?
The size of the gap relative to the wavelength.
What happens when the gap is much wider than wavelength?
Little diffraction.
What happens when the gap is a bit wider than wavelength?
Diffraction only occurs at edges.
What happens if the gap is the same as the wavelength?
Maximum diffraction.
What affects how much a wave diffracts by?
The longer the wave, the more they diffract and bend around.
What does information have to be converted to before it is transmitted over long distances?
Electrical signals.
What happens to these electrical signals?
They can be sent down telephone wires or carried on EM waves.
What can signals be?
Analogue or digital.
What is analogue signal?
Signal that can take any value with a certain range.
What is the amplitude and frequency of analogue waves?
They can vary continuously.
What are digital signals?
They can only take two values.
What do signals do as they travel?
They weaken.
What needs to be done to signals along their route?
They need to be amplified.
What do signals pick up?
Interferences or noise from electrical disturbances or other signals.
What happens when analogue signals are amplified?
The noise is amplified too so every time it is amplified the signal loses quality.
What is different about digital signals when they are amplified?
The noise is ignored so the signal remains high quality.
What happens when two or more waves of a similar frequency meet?
They can create one combined signal with a new amplitude. This is called interference.
When does interference occur?
When two radio stations transmit on similar frequencies.
How is it easier to transmit digital signals?
Using one cable or EM wave, called multiplexing.
What is quantisation?
The process of rounding multiple values to a smaller set.
What does quantisation allow?
You can pack more information into the same amount of space.
How does quantisation work with digital signals?
Because they only have two values quantisation doesn’t lose much information.
How does quantisation work with analogue signals?
A lot of information is lost when a continuous range is rounded off.
What can pick up sound waves travelling through the air?
A sound wave receiver such as a microphone.
What can a oscilloscope do when plugged into a sound wave receiver?
Display the waves and measure their properties.
What does an oscilloscope do?
Converts sound waves to electrical signals.
What is an oscilloscope?
A device which can display the microphone signal as a trace on a screen.
What does the appearance of the wave on the screen tell?
Whether the sound is loud or quiet, high or low pitched.
What does greater amplitude mean?
The more energy it carries, louder.
What will louder sound have on an oscilloscope?
A larger amplitude.
What is frequency?
The number if complete vibrations each second.
What is frequency measured in?
Hz.
How can you compare the frequency of a waves?
An oscilloscope.
If the sound vibrates with a higher frequency, what is the sound?
A high-pitch.
If the sound vibrates with a low frequency, what is the sound?
Low-pitched.
On an oscilloscope what does the horizontal axis do?
Display time.
How can you measure frequency on an oscilloscope?
- Adjust the time division setting until the display shows at least 1 complete cycle.
- Read off the period.
- Frequency = 1/time period
