physics from book

Question 1

what is a wavelength

Answer 1

distance from one point on a wave to the next identical point on the wave

Question 2

what is amplitude

Answer 2

maximum displacement from the rest position

Question 3

what is frequency

Answer 3

how many waves pass a point every second

Question 4

what is time period

Answer 4

time it takes for one wave to pass

Question 5

what is phase difference

Answer 5

difference in phase between two waves with the same frequency and wavelength

Question 6

what is transverse

Answer 6

wave where the particles are displaced at 90 degrees to the direction of energy transfer

Question 7

what is longitudinal

Answer 7

a wave in which the particles are displaced paroled to the direction of energy transfer

Question 8

examples of transverse waves

Answer 8

ripples on the surface of water , vibration son guitar strings, light waves.

Question 9

examples of longitudinal waves

Answer 9

sound waves , ultrasound waves

Question 10

what is reflection

Answer 10

when a wave bounces off an object and changes direction . The angle of incidence = the angle of reflection

Question 11

what is refraction

Answer 11

bending of a wave as it passes from one medium to another

Question 12

why do submerged objects appear shallower than they are

Answer 12

light from them changes angle at the surface , bending downwards towards the water

Question 13

what is diffraction

Answer 13

diffraction occurs when an object causes a wave to change direction and bend around it

Question 14

what is constructive interference

Answer 14

waves combine without any phase difference. When they oscillate out of phase

Question 15

what is destructive interference

Answer 15

waves combine differing by multiples of 1/2 wavelengths , they oscillate

Question 16

what is dispersion

Answer 16

separation of visible light into its different colours

Question 17

what is emission spectra

Answer 17

1. heat up or pass a current through an element
2. some electrons become excited and move to higher energy levels
3. the electrons loose energy and move back down to ground state
4. light can be split up using a diffraction gratting to create a unique pattern

Question 18

what is resonance

Answer 18

a phenomenon that occurs when an object or system is subjected to an external force of vibration

Question 19

what is a progressive wave

Answer 19

wave motions that transfer energy as the crests move through space

Question 20

what is a stationary wave

Answer 20

wave motions that sore every as the wave crests remain still

Question 21

what is a node

Answer 21

points along a stationary wave where the amplitude is minimum

Question 22

what is antinode

Answer 22

points along a stationary wave where the amplitude is at its maximum

Question 23

what is coherent

Answer 23

waves that have the same frequency and wavelength and therefore a constant phase difference

Question 24

the angle of incidence equals

Answer 24

the angle of reflection

Question 25

the speed of light in vacuum is given what letter

Answer 25

c

Question 26

why does light slow down when it travels through a transparent material

Answer 26

the electronic charges in the material interfere with the EM waves , which causes it to change direction

Question 27

refractive index =

Answer 27

speed of light in a vacuum divided by speed of light in a medium

Question 28

what happens to the energy when light leaves the block

Answer 28

some of the energy may not be able to leave and is reflected back into the block

Question 29

what happens when the angle in the glass between the ray and the normal lines is increased to a critical angle

Answer 29

refracted ray is bent so far it turns along the glass air boundary = 90 degrees

Question 30

what happens when the angle of incidence is greater than the critical angle

Answer 30

ray is reflected internally and there is no refracted beam at all = total internal reflection

Question 31

when does total internal reflection take place

Answer 31

when light travels from a medium that has a higher n to a medium with a lower n

Question 32

sin c

Answer 32

1/n

Question 33

n =

Answer 33

1 / sin c

Question 34

refraction

Answer 34

I < c

Question 35

critical angle

Answer 35

I = c

Question 36

TIR

Answer 36

I> C

Question 37

what are optical fibres

Answer 37

long thin cylinders of glass or plastic

Question 38

what happens when light is fed into the cut end at angles greater than the critical angle

Answer 38

all the rays of light get totally internally reflected along the length of the fibre , no wave energy is lost but a small amount is absorbed

Question 39

how are optical fibres used in medicine?

Answer 39

1) endoscopes 2) inserted into the body to view internal organs 3) keyhole surgery light is fed into the body through a small number of optical fibres , the image is returned via another set of optical fibres same with then lenses. The image is pixelated as each fibre produces one dot of information

Question 40

how are fibre optics used in communication

Answer 40

analogue signals , they are continuous signals that represent physical measurements , they can weaken over distances , cannot be stored easily

Question 41

how are digital signals represented

Answer 41

binary

Question 42

how are digital signals better than analogue

Answer 42

- can be flashes of light , so they can be the same intensity which means there is less chance of weakening . They can be stored easily

Question 43

How do you convert analogue to digital

Answer 43

- done by an ADC -transducer is used to produce an analogue electrical voltage signal - this is connected to an ADC -ADC samples the analogue signal produce voltage time graph -sampling rate is determined , this is the interval the ADC samples the analogue signal . The greater the sampling rate the more accurate the digital signal will be -sensitivity of conversion is determined , this is the smallest difference which can be sent in digital signal. -ADC is connected to a transmitter which sends the digital signal in a series of 1 and 0 bursts along the optical fibre

Question 44

What is broadband

Answer 44

Indicates the speed and carrying capacity of a data channel - signals sent along optical fibres are in the form of light - there are many different wavelengths of light which have a different frequency - frequency bonds -each bond can carry a separate channel of data -they can be sent along the optical fibre at the same time - the number of frequency bonds that are sent is called the band width -achieved by wave division multiplexing