Physics Definitions - Light/waves/sound

Front 1

State laws of reflection

Back 1

1) Incident ray, reflected ray, and normal at the point of incidence all lie in the same plane

2) Angle of incidence i = angle of reflection r

Hint 1

Remember light rays that strike on a mirror

Front 2

Characteristics of a plane mirror image

Back 2

1) Image is same size as object

2) Lterally inverted

3) Upright

4) Virtual

5) Distance from mirror to image = distance from mirror to object

Front 3

Uses of mirrors

Back 3

- Vision testing (make letters and numbers appear further away)

- Blind corner mirror

- Instrument scale (Voltmeter - avoid parallex error)

- Periscope

- Teleprompter (Newsreading)

- others : optical instruments like telescopes, overhead projectors, CD players

Front 4

Define refraction

Back 4

The bending of light as light passes from one optical medium to another

(Due to the change in speed of light at the boundary of the two different optical media)

Front 5

State laws of refraction

Back 5

1) Incident ray, refracted ray, and normal all lie in the same plane

2) For 2 given media, the ratio if the sine of angle of i to the sine of angle of r is a constant.

n= sin i/ sin r

Front 6

Define optical centre

Back 6

Midpoint between surfaces of lens on its principal axis

Rays passing through optical centre are not refracted

Front 7

Define principal axis

Back 7

Horizontal line passing through optical centre of lens , perpendicular to vertical plane of lens

Front 8

Uses of converging lenses

Back 8

- Magnifying glass

- Liquid Crystal Display ( LCD) projector

- Film camera

- Visual correction for long sightedness ( 老花眼）

Front 9

Define a wave

Back 9

A wave is a disturbance that transfers energy from one place to another without transferring matter during energy transfer.

[A wave is made up of periodic motion (Periodic motion is motion repeated at regular intervals) ]

Front 10

Define transverse waves

Back 10

Waves that travel perpendicular to the direction of the vibration

Front 11

Define longitudinal waves

Back 11

Waves that travel parallel to the direction of the vibration

Front 12

Define amplitude

Back 12

Maximum displacement of a point from its rest position

Front 13

Define wavelength

Back 13

Shortest distance between any 2 points in phase

Front 14

Define wavefront

Back 14

An imaginary line on a wave that joins all adjacent points that are in phase

Front 15

Period of wave

Back 15

Time taken for 1 complete wave

Front 16

Refractive index

Back 16

Ratio if speed of light in vacuum to speed of light in the medium.

n = c/v

Front 17

Frequency of wave

Back 17

The number of complete waves per second (Hz)

Front 18

Define Total internal reflection

Back 18

The complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium.

Front 19

Conditions for TIR

Back 19

1) Light ray in optically denser medium strikes its boundary with an optically less dense medium

2) angle of i > angle of c of the optically denser medium.

Front 20

Define critical angle

Back 20

The angle of i in an optically denser medium for which angle of refraction in the optically less dense medium is 90deg

Front 21

Formula to find critical angle

Back 21

Sin c = 1/n

n = 1/sin c

Front 22

Uses of TIR

Back 22

1) Glass prisms

- Binoculars

- Periscopes

- Single lens reflex cameras

2) Optical fibres

• Telecommunications industry

:) - Higher carrying capacity compared to copper wire

- Less signal degredation compared to copper wire

- lightweight

- low cost

• Medical industry

:)- High flexibility, use as endoscopes to see inside hollow organs like intestines

Front 23

Define focal length **

Back 23

f is the distance between optical centre C and focal point F

Front 24

Define focal plane

Back 24

The plane that passes through focal point F and perpendicular to principal axis

Front 25

Define focal point F

Back 25

The point at which all rays parallel to principal axis converge after refraction by lens

Front 26

Wave speed v=f入

Back 26

Distance travelled by a wave per second

Front 27

Order of Electromagnetic spectrum

(lowest to highest frequency)

(longest to shortest wavelength)

Back 27

Radio waves

Microwaves

Infrared

Visible light (red to purple)

Ultraviolet

X-rays

Gamma rays

Front 28

Properties if EM waves

Back 28

- Transverse waves

- Can travel through vacuum

- Transfer energy from one place to another

- Travel at same speed of 3 x 10^8 m/s in vacuum

- v=f入 applicable

- Travelling from one medium to another, V and 入 change. f does not change.

- Obeys laws of reflection/ refraction

- Carry no electric charge

Front 29

Applications of EM waves

Back 29

Radio:

- radios

Microwave:

- microwaves ovens, satellite tv, GPS (global positioning system)

Infrared radiation:

- Remote controllers, ear thermometers, intruder alarms

Visible light:

- optical fibres

UV radiation:

- Sunbeds, sterilisation of equipment

X-rays:

- Radiation therapy (kill cancer cells), airport detection imaging

Gamma rays:

- Radiation therapy (treat cancer by killing cancer cells)

Front 30

Define sound

Back 30

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 31

Define sound

Back 31

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 32

How do sound waves propagate ?

Back 32

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 33

Define sound

Back 33

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 34

How do sound waves propagate ?

Back 34

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 35

Can sound be transmitted through vacuum? Why?

Back 35

No. Sound waves need a medium to travel. Like EM waves.

Front 36

Define sound

Back 36

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 37

How do sound waves propagate ?

Back 37

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 38

Can sound be transmitted through vacuum? Why?

Back 38

No. Sound waves need a medium to travel. Like EM waves.

Front 39

Speed of sound in S/L/G

Back 39

Gas -> Liquid -> Solid

Slowest ---> Fastest

Front 40

Define sound

Back 40

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 41

How do sound waves propagate ?

Back 41

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 42

Can sound be transmitted through vacuum? Why?

Back 42

No. Sound waves need a medium to travel. Like EM waves.

Front 43

Speed of sound in S/L/G

Back 43

Gas -> Liquid -> Solid

Slowest ---> Fastest

Front 44

Define echo?

Back 44

Repetition of sound due to reflection of sound.

Front 45

Define sound

Back 45

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 46

How do sound waves propagate ?

Back 46

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 47

Can sound be transmitted through vacuum? Why?

Back 47

No. Sound waves need a medium to travel. Like EM waves.

Front 48

Speed of sound in S/L/G

Back 48

Gas -> Liquid -> Solid

Slowest ---> Fastest

Front 49

Define echo?

Back 49

Repetition of sound due to reflection of sound.

Front 50

Formula of speed of sound involving echo

Back 50

v = 2d / t

Front 51

Define sound

Back 51

Form of energy that is transferred from one point to another as a longitudinal wave.

Front 52

How do sound waves propagate ?

Back 52

- Compressions (regions where air pressure is higher than surrounding air pressure)

- Rarefactions ( regions where air pressure is lower than surrounding air pressure)

Front 53

Can sound be transmitted through vacuum? Why?

Back 53

No. Sound waves need a medium to travel. Like EM waves.

Front 54

Speed of sound in S/L/G

Back 54

Gas -> Liquid -> Solid

Slowest ---> Fastest

Front 55

Define echo?

Back 55

Repetition of sound due to reflection of sound.

Front 56

Formula of speed of sound involving echo

Back 56

v = 2d / t

Front 57

Uses of echoes

Back 57

- Measure large distance

- detect location if objects

Front 58

Define ultrasound

Back 58

Sound with frequencies above upper limit of human range of audibility ( 20 000Hz)

Front 59

Define ultrasound

Back 59

Sound with frequencies above upper limit of human range of audibility ( 20 000Hz)

Front 60

Uses of ultrasound

Back 60

- Quality control to check for cracks in concrete slabs

- Prenatal scanning

Front 61

Define ultrasound

Back 61

Sound with frequencies above upper limit of human range of audibility ( 20 000Hz)

Front 62

Uses of ultrasound

Back 62

- Quality control to check for cracks in concrete slabs

- Prenatal scanning

Front 63

Define pitch

Back 63

Related to frequency of sound wave

Higher frequency, higher pitch

Front 64

Define Loudness

Back 64

Related to amplitude of sound wave

Larger amplitude, louder the sound.

Front 65

Define wave speed

Back 65

V is the distance travelled by a wave per second