Light

Question 1

what is visible light

Answer 1

a form of energy that is part of the electromagnetic spectrum

Question 2

what does the ray model of light show

Answer 2

the straight-line path of light with arrows for direction

Question 3

what are the types of light rays

Answer 3

parallel convergent divergent

Question 4

what are luminous objects

Answer 4

objects that emit light in all directions e.g. sun lamps fireflies

Question 5

what are non-luminous objects

Answer 5

objects that do not emit light but reflect light e.g. moon humans

Question 6

what is visible light in terms of spectrum

Answer 6

the small part detectable by human eyes

Question 7

what is white light

Answer 7

polychromatic light made of all rainbow colours

Question 8

why do objects appear coloured

Answer 8

they absorb some colours and reflect others

Question 9

what is reflection of light

Answer 9

the bouncing of light off a surface allowing us to see non-luminous objects

Question 10

what causes the colour of an object

Answer 10

the way it reflects or absorbs colours of light

Question 11

what colour does an object appear if it reflects all colours

Answer 11

white

Question 12

what colour does an object appear if it absorbs all colours

Answer 12

black

Question 13

what are pigments

Answer 13

chemicals that absorb specific colours of visible light

Question 14

what colours are the primary colours of light

Answer 14

red green blue

Question 15

what colour is formed when red and green mix

Answer 15

yellow

Question 16

what colour is formed when red and blue mix

Answer 16

magenta

Question 17

what colour is formed when green and blue mix

Answer 17

cyan

Question 18

what are characteristics of images in plane mirrors

Answer 18

same size upright laterally inverted virtual perpendicular object distance is equal to the perpendicular image distance from the plane mirror

Question 19

what is the incident ray

Answer 19

the light ray hitting a reflecting surface

Question 20

what is the normal

Answer 20

line perpendicular to the surface at point of incidence

Question 21

what is the angle of incidence

Answer 21

angle between incident ray and normal

Question 22

what is the angle of reflection

Answer 22

angle between reflected ray and normal

Question 23

what is the reflected ray

Answer 23

ray travelling away from the reflecting surface after bouncing

Question 24

what are the laws of reflection

Answer 24

incident ray reflected ray and normal lie in the same plane and angle of incidence equals angle of reflection

Question 25

what happens in regular reflection

Answer 25

parallel rays hit a smooth surface reflect evenly and form clear images

Question 26

what happens in diffused reflection

Answer 26

rays hit rough surface reflect in many directions and image is unclear

Question 27

what are plane mirrors used for

Answer 27

periscopes instrument scales avoiding parallax error

Question 28

what are concave mirrors

Answer 28

inward curved mirrors forming virtual upright magnified images used in headlights solar devices dentistry

Question 29

what are convex mirrors

Answer 29

outward curved mirrors forming virtual upright diminished images used as rear-view mirrors surveillance mirrors road safety

Question 30

what must be shown in ray diagram construction

Answer 30

reflecting surface normal dotted virtual rays solid incident rays and correct angle labels

Question 31

what is refraction of light

Answer 31

bending of light when it passes between media of different optical density

Question 32

when does light bend towards the normal

Answer 32

when entering a medium of higher optical density

Question 33

when does light bend away from the normal

Answer 33

when entering a medium of lower optical density

Question 34

what are conditions for refraction

Answer 34

light passes between different media and angle of incidence is more than 0

Question 35

what is refractive index

Answer 35

the ratio of speed of light in vacuum to its speed in a medium n=c/v

Question 36

what is the speed of light in vacuum

Answer 36

3.00 x 10^8 m/s

Question 37

what does a higher refractive index mean

Answer 37

the material is more optically dense and slows light more

Question 38

what is dispersion of light

Answer 38

splitting of white light into seven colours due to different refraction angles

Question 39

what are the seven colours of the spectrum

Answer 39

red orange yellow green blue indigo violet

Question 40

what are applications of infrared radiation

Answer 40

thermal imaging remote controllers intruder alarms

Question 41

what are harmful effects of infrared radiation

Answer 41

eye damage and contribution to global warming

Question 42

what are applications of visible light

Answer 42

photosynthesis vision optical fibres in medicine and telecommunications

Question 43

what are harmful effects of visible light

Answer 43

chemical changes deterioration light pollution affecting wildlife

Question 44

what are applications of ultraviolet radiation

Answer 44

production of vitamin d disinfecting equipment food and water

Question 45

what are harmful effects of ultraviolet radiation

Answer 45

eye damage and skin cancer