Light and Optics Grade 8

angle of incidence

the angle between the incident ray and the normal

angle of reflection

The angle between the reflected ray and the normal

angle of refraction

the angle between the normal and the refracted ray

artificial light source

a human made light source

bioluminescence

the emission of light produced by chemical reactions inside the bodies of living creatures

concave

curving inward and forms larger virtual images

convex

curving outward and forms smaller virtual images

fluorescence

The process in which high energy, invisible ultraviolet light is absorbed by the particles of an object, which then emits some of this energy as visible light, causing the object to glow.

image

the likeness of an object

incandescent source

an object that can be heated to such a high temperature that it emits visible light

incident ray

the light that strikes a reflecting or refracting

light

a visible form of energy, that either radiates outward from a source in all directions, reflects off different objects into our eyes, can travel through empty space

the first basic principle of light

when light reaches a surface, it can be absorbed and transformed into other forms of energy, amount of energy absorbed dependent on light intensity

phosphorescent

light energy is absorbed by particles, stored and is later emitted as visible light

chemiluminescent

light energy released by chemical reactions

LED'S

light emitting diode. They require less energy, lose minimal energy

the ray model of light

the path a beam of light travels can be represented by straight lines called rays. Light travels in a straight line until it strikes a surface.

how will a transparent material act if light strikes?

light will move through undeflected

how will a translucent material act if light strikes?

light will deflect after moving through

how will a opaque material act if light strikes?

light will be absorbed by the object

reflection

process in which light strikes a surface and bounces back

law of reflection

the angle of incidence is equal to the angle of reflection

virtual image

the image you see in a mirror

refraction

process in which the speed of light changes when it travels from one medium to another

what happens to light when it enters a a less dense medium?

light speeds up. ex: water to air

what happens to light when it enters a denser medium?

light slows down. ex: air to water

law of refraction

when light travels from one medium into a denser one, it will bend towards the normal line. less dense one, it will bend away from the normal line

what happens when light hits a surface? absorption

occurs mostly on rough, dark, opaque surfaces

what happens when light hits a surface? reflection

light bounces off surface and changes direction. occurs mostly on shiny, smooth surfaces

what happens when light hits a surface? refraction

light travels through the surface, often in a different direction. occurs when light strikes a different transparent medium

pupil

the opening through which light enters the eye

iris

coloured ring surrounding the pupil. expands or contracts the pupil depending on the brightness of the light

cornea

transparent surface that covers the pupil and iris. refracts light to a small degree

aqueous humour

fluid between the iris and cornea. keeps the eyeball rigid and refracts light

retina

layer of the eye that contains photoreceptors which detect light

lens

focuses the image on the retina

vitreous humour

fluid in the centre of the eye that helps keep its shape

ciliary muscle

adjusts the thickness of the lens to focus on near or far objects

optic nerve

transmits signals from light receptors in the retina to the brain

near sightedness

difficulty in seeing distant objects, occurs when an eye is too long, image forms in front of the retina, corrected using a concave lens

far sightedness

difficulty in seeing close objects, occurs when an eye is too short, image forms in behind of the retina, corrected using a convex lens

luminous

giving off light

natural light source

the non human made source of light such as the sun

non luminous

Does not produce its own light

normal

a reference line drawn perpendicular to a reflecting surface at the point where an incident ray strikes the surface

opaque

not allowing any light to pass through

plane

a flat or level surface

radiant energy

energy transferred or emitted as waves or rays in all directions

radiates

to send out energy in the form of waves or rays

radiation

the transfer of radiant energy, such as light

reflected ray

the light that is cast back from a reflecting surface

translucent

allowing some light to pass through

transparent

allowing light to pass through

iris reflex

when the pupil dilates or contracts to allow more or less light into the eye

refracting telescope

a telescope that uses convex lenses to gather and focus light

reflecting telescope

a telescope that uses a curved mirror to collect and focus light

shutter

a device that opens and closes in front of the lens of a camera

additive primary colors

red, green, blue

amplitude

height of a wave

colour blindness

it's when your cones and rods aren't able to function properly. It forms the inability to process the colours red and green

complementary colors

colors located directly opposite one another on the color wheel

cones

the cones detect fine detail and give rise to color sensations.

rods

retinal receptors that detect black, white, and grey

secondary colors

orange, green, violet

wave model of light

a model of light behaviour that represents light travelling as a wave

wavelength

horizontal distance between the crests or between the troughs of two adjacent waves

x-rays

electromagnetic waves with wavelengths shorter than ultraviolet rays, but longer than gamma rays