Waves and Light Definitions

Question 1

Normal

Answer 1

Force acting at right angles to a surface.

Question 2

Pressure

Answer 2

Force perpendicular to surface per unit area.

Question 3

Amplitude

Answer 3

Maximum displacement of a wave from equilibrium.

Question 4

Diffraction

Answer 4

Bending of waves around gaps/edges.

Question 5

Frequency

Answer 5

Number of waves per second (1/period).

Question 6

Longitudinal wave

Answer 6

Oscillations parallel to wave direction AND consists of compressions and rarefactions

Question 7

Reflection

Answer 7

Bouncing back of waves at boundaries.

Question 8

Refraction

Answer 8

Change in direction of a wave due to change in wave speed and wavelength when crossing mediums.

Question 9

Speed of a wave

Answer 9

Distance travelled by wave point per time.

Question 10

Transverse wave

Answer 10

Oscillations perpendicular to wave direction AND consists of crests and troughs

Question 11

Water wave

Answer 11

Waves on water surface.

Question 12

Wavefront

Answer 12

Surface where all points have the same wave propeties

Question 13

Wavelength

Answer 13

Distance between equivalent points on adjacent waves. (2 consecutive crests/troughts OR compressions/rarefactions)

Question 14

Angle of incidence

Answer 14

Angle between incident ray and normal.

Question 15

Angle of reflection

Answer 15

Angle between reflected ray and normal.

Question 16

Optical image

Answer 16

Apparent reproduction of an object by lenses or mirrors.

Question 17

Plane mirror

Answer 17

Flat reflective surface forming virtual image

Question 18

Critical angle

Answer 18

The angle of Incidence where a refracted angle of 90 is produced. (beyond which total internal reflection occurs)

Question 19

Optical fibre

Answer 19

Flexible glass core transmitting light by total internal reflection.

Question 20

Refractive index

Answer 20

Ratio of light speed in vacuum to that of light traveling in a medium. lowest n = 1

Question 21

Total internal reflection

Answer 21

When all light is reflected and none is refracted, occurs when angle of incedence > critical angle AND when light travels from denser to rarer medium

Question 22

Diminished

Answer 22

Made smaller.

Question 23

Enlarged

Answer 23

Made larger.

Question 24

Focal length

Answer 24

Distance from lens centre to principal focus.

Question 25

Long-sightedness (Far-sight)

Answer 25

Blurry near objects; corrected with convex lenses.

Question 26

Magnifying glass

Answer 26

A convex lens used to enlarge images. (Focal length of object < 1f)

Question 27

Principal focus

Answer 27

Point where rays traveling parallel to the lens converge.

Question 28

Real image

Answer 28

Image that can be formed on a screen, are formed by light comming from object.

Question 29

Short-sightedness (near-sightedness)

Answer 29

Blurry distant objects; corrected with concave lenses.

Question 30

Virtual image

Answer 30

Image that cannot be formed on a screen, only appear to be formed by light comming from object.

Question 31

Dispersion

Answer 31

Splitting white light into spectrum.

Question 32

Glass prism

Answer 32

Transparent element refracting light.

Question 33

Monochromatic light

Answer 33

Single frequency light.

Question 34

Spectrum

Answer 34

Range of electromagnetic wavelengths/frequencies.

Question 35

Electromagnetic spectrum

Answer 35

Transverse waves covering a range of frequencies/wavelengths; γ-rays highest frequency

Question 36

Uses of Infrared radiation

Answer 36

Cooking

Question 37

Uses of Microwaves

Answer 37

Satellite communications

Question 38

Uses of Radio waves

Answer 38

TV/radio signals; produced or induce circuit oscillations.

Question 39

Vacuum

Answer 39

Space devoid of matter.

Question 40

Uses of X-rays

Answer 40

Medical imaging

Question 41

Audible frequencies

Answer 41

20 Hz–20 000 Hz.

Question 42

Compressions

Answer 42

High-pressure regions in longitudinal waves where particles are close together.

Question 43

Echo

Answer 43

Reflected sound wave.

Question 44

Loudness

Answer 44

Amplitude of oscillations.

Question 45

Pitch

Answer 45

Frequency of oscillations.

Question 46

Rarefactions

Answer 46

Low-pressure regions where particles are far apart.

Question 47

Sound waves

Answer 47

Longitudinal (consist of compressions and rarefactions) vibrations requiring a medium to travel.

Question 48

Speed of sound

Answer 48

Distance per time travelled by sound wave.

Question 49

Ultrasound waves

Answer 49

Waves with a frequency greater than 20 kHz that are inaudible to humans.