Combined Waves Topic Vocabulary

Question 1

Angle of reflection

Answer 1

the angle between the reflected ray and the normal

Question 2

Angle of incidence

Answer 2

the angle between the normal and the incident ray

Question 3

Angle of refraction

Answer 3

the angle between the refracted ray and the normal

Question 4

Snell’s Law

Answer 4

when an incident ray passes into a material: n = sin i ÷ sin r

Question 5

Law of reflection

Answer 5

in reflection at a surface, the angle of incidence is equal to the angle of reflection

Question 6

Diffraction of waves

Answer 6

when waves meet a gap in a barrier, they carry on through the gap, but the waves spread out to some extent into the area beyond the gap

Question 7

Dispersion of white light

Answer 7

when white light passes through a prism, it splits into different spectral colours and wave lengths (dispersion) and the different colours of the spectrum seperate

Question 8

Refraction

Answer 8

light waves change speed when they pass across the boundary between two differenct media

this causes them to change direction

Question 9

Reflection

Answer 9

there is reflection when waves bounce off a surface

Question 10

Real image

Answer 10

produced when real rays of light cross and can be projected

Question 11

Virtual image

Answer 11

produced when virtual rays of light cross

can’t be projected

it is the same size, laterally inverted and the same distance beyond the mirror as the real image

Question 12

Transverse Wave

Answer 12

produced when the vibrations are perpendicular to the direction of energy

e.g. light waves

Question 13

Longitudinal wave

Answer 13

produced when the vibrations are parallel to the direction of energy

e.g. sound waves

Question 14

Refractive index

Answer 14

refractive index (n) = speed of light in air (3x10⁸) ÷ speed of light in material

Question 15

The electromagnetic spectrum

Answer 15

a continuous range of wavelengths

Question 16

Frequency

Answer 16

the number of vibrations (or waves) per second in Hertz (Hz)

Question 17

Wavelength

Answer 17

the shortest distance between two parts of a wave that are in phase (doing the same thing)

Question 18

Amplitude

Answer 18

the distance from the centre of a wave to the peak or trough

Question 19

Speed of light

Answer 19

the distance light can travel in a unit of time through a given substance

Question 20

Speed of light in air

Answer 20

3x10⁸ m/s

Question 21

Speed of sound in air

Answer 21

343 m/s

Question 22

Echo

Answer 22

a sound caused by the reflection of sound waves from a surface back to the listener

Question 23

Ultrasound

Answer 23

sound with a frequency greater than 20,000Hz (20 kHz)

this is above the range of human hearing

Question 24

Reliability

Answer 24

a set of results that are repeated and the spread of the readings is small (or they cluster together)

Question 25

Validity

Answer 25

an experiment is valid if you measured what you set out to investigate

Question 26

Fair test

Answer 26

a test in which only the independent variable has been allowed to affect the dependent variable e.g. by keeping all other variables constant

Question 27

Parallax error

Answer 27

caused by not having the eye in line with the object being measured and the scale being measured against

Question 28

Human error

Answer 28

humans making small mistakes when taking readings

this can be minimised by good experimental technique and repeating readings

Question 29

Random error

Answer 29

produced either side of the true value

caused by human error or unknown and unpredictable changes in the experiment (e.g. measuring instruments or in the environmental conditions)

Question 30

Precision

Answer 30

the result of using the correct piece of equipment with appropriate resolution or smallest division

precise measurement are ones in which there is very little spread about the mean value

Question 31

Accuracy

Answer 31

reliable and precise measurements can produce results very close to the true value and therefore be accurate