applied science btec unit 1: physics

Define the amplitude of a wave

The distance from the rest position to the top of the wave

Define the period of a wave

The time taken for one wavelength to pass a point

Define the frequency of a wave

The number of waves per second

How many ms are in 1s?

1000

Define coherent light

Coherent light has the same frequency/wavelength and is in phase

Define a transverse wave

The oscillations are perpendicular to the direction of travel

Define a longitudinal wave

The oscillations are parallel to the direction of travel

How many radians are in 360 degrees?

2 pi

Define phase difference

Phase difference shows how much two waves are in line with each other. Measured in fractions or degrees

What is constructive interference?

When two waves in phase add together to make a larger amplitude wave

What is destructive interference?

When two waves in antiphase cancel each other out

How do you make a standing wave?

A wave is transmitted along a string, reflects back and the two waves superimpose with each other

What is coherent light?

light of the same wavelength that is in phase

What is refraction?

When light charges from one media to another and charges angle and direction because it slows down

What is total internal reflection?

When light reflects internally inside a piece of glass rather than refracting out because the angle of incidence is above the critical angle

What is an emission spectra?

Wavelengths of light emitted by electrons. They can be used to identify elements

What is an endoscope?

A medical tool that uses total internal reflection to see inside a body without surgery

What is the difference between single mode and multi mode fibres?

Single mode has a thin core and carries less information a longer distance. Multi mode is suitable for LAN as it carries lots of signals but not far

State the EM spectrum in order

Radio waves

Microwaves

Infrared radiation

Visible light

Ultraviolet

X-rays

Gamma rays

State the properties of radio waves

Long wavelength, low energy, refract off the atmosphere, used for communications

State the properties of microwaves

Shorter wavelength than radio waves, transmit through the atmosphere, used for phones and satellites

State the properties of infrared radiation

Thermal radiation, used in remote control, requires direct line of sight, easily absorbed so short distance only

Explain the inverse square law for radiation

If the distance from an EM wave source double, the intensity drops to a quarter of the previous intensity

What is micro in standard form?

10-6

What is nano in standard form?

10-9

Define oscillation

Regular variation in magnitude or position about a central point

Define displacement

How far the quantity that is in oscillation has moved from its mean value at any given time

Wave speed equation

wave speed = frequency x wavelength

Define diffraction

The tendency of a wave to spread out in all directions, transferring energy to its surroundings as it does

Define diffraction grating

It is a flat plane objects, it has a series of regular lines formed on it that block parts of na advancing wave front

Define superposition

The adding together of wave displacements that occurs when waves from two or more separate sources overlap at any given location in space, the displacement simply add mathematically

Define path difference

Is the difference in the length between two rays

Describe gratings in reflection mode

Instead of looking at what comes through a grating, you look at the part of the wave energy that is bounced back off the grating surface

Because he grating lines are regularly spaces and interference patten is produced

Describe coherent light sourced

When light is emitted from or absorbed by matter, you can only explain what happens by thinking of light as being composed of tiny particles called photons

When thinking about the coherence of light, you have to combine ideas from wave theory

with the idea of individual photons particles called wave particle duality

Define emission spectra

The quantum theory of light and other electromagnetic radiations is based on the experimental observation that there is a simple relationship between the frequency of the radiation and the energy by each photon

Define resonance

The storing of energy in an oscillation or a stationary wave, the energy coming from an external source of appropriate frequency

Refractive index equation

Speed of light in a vacuum/Speed of light in the medium

How are fibre optics used in medicine?

Endoscopes are inserted into a body organ though an opening

Endoscopes are also used in keyhole surgery to guide the use of surgical instruments with remote handling

What is an optical fibre?

It's a long thin cylinder of glass or plastic

Light is fed into the cut end of the fibre so when it hits the sides of the fibre it almost always does so at angles greater than the critical angle. That means all the rays of light get totally internally reflected and keep bouncing down the length of the fibre

How are optical fibres used for analogue signals?

The electrical signals made by a microphone which mimic the shape and intensity of the sound waves they are detecting

The position of the pointer on a pressure dial gauge

The waveform displayed on a cathode day oscilloscope, which copies and shows the variation of an AC voltage with time

How are optical fibres used for digital signals?

Digitising information not only makes it possible to send more data faster using analogue transmission. It also makes the transmission much more reliable and interference free

Converting a signal from analogue to digital is carried out electronically using an analogue to digital converter

How are fibre optics broadband networks used in boardbands?

Used to indicate the speed and carrying capacity of a data channel.

In connection with the internet it has been used to market the improvement from earlier telephone dial up connections, which were very limited and slow.

Fibre optic board and has been progressively replacing copper cable connection with consequent gains in data speed

How are fibre optics broadband networks used in multi mode fibres?

Is the standard fibre cable used for sending optical signals over short to medium distances

How are fibre optics broadband networks used in single mode fibres?

Has a narrower core which is less than ten wavelengths of the infrared light that is used in them.

This means there is just no space for different beams travelling at different angles down the core.

Instead the light wave moves as a single wave front straight down the centre of the fibre and all the signal energy reaches the far end of the fibre at the same instant.

Millions of kilometres of this high quality cable is laid every year to build the fibre optic networks for phones, tv and board and internet connections

Define analogue signal

A signal whose strength is proportional to the quantity it is representing

Define digital signal

Conveys in binary code a number that represents the size of the measured quantity