revision Flashcards
what is reflection?
when light bounces off a surface
what surfaces reflect
usually opaque and translucent surfaces
define translucent, transparent, and opaque
transparent=light can go fully go through the substance
translucent=some light can go through a substance
opaque=no light can pass through
define luminous and non luminous
a luminous object is one that makes and gives off its own light
a non-luminous object is one that does not make its own light
what is the incident ray
is the in going beam of light hat hits the mirror
what is the reflected ray
beam of light that bounces off the mirror
what is the angle of incidence
between the incidence ray and the normal
angle of reflection
angle between the reflected ray and the normal
what is the law for reflection
angle of incidence = angle of reflection (I=r)
what is refraction
is when light bends at a surface between two different substances.
in refraction when is a ray bent towards the normal?
light rays bend towards the normal when light travels from a less dense to a more dense substance e.g. air into glass or air into water
in refraction when is a ray bent away from the normal
light bends away from the normal when light travels from a more dense to a less dense substances e.
what type of lens is diverging? converging?
convex is converging-light beams come together
concave is diverging=light beams move apart
what are the colours in the visible spectrum
ROYGBIV
Visible spectrum energy
red=low ow frequency through to violet which is high frequency/energy
what is the speed of light
300,000 km/sec
what is a light year
a light year is the distance light can travel in one year
how far does light travel in air in one hour
300,000 x 60 x 60 = 1,080,000,000
what is a photon and how is it made
a photon is a small packet of energy. It is made when electrons in an atom are energized by an external source of energy such as heat, electricity, light , UV, and gets `excited’ and jump up one electron shell. As they fall back they release a bit of extra energy as a photon of light
list different forms of energy that can excite electrons in atoms to make photons
heat, electricity, light, UV
what kind of wave is an electromagnetic wave
transverse
what is the wave equation
v=flanda
what is the velocity(speed)
how fast the wave is travelling measured in metres per second
what is wave frequency
is the number of waves that pass a particular point every second. it is measured in hertz
what is the wavelength
is the distance from the peak of one wave to the peak of the next wave measured in metres
what is the wave amplitude
height of the wave from top to bottom measured in metres
how does an eye use a lens to focus light
light passes through the pupil and into the lens. As it passes through the lens which is convex shape, the light is converged onto the back of the eye. the retina where it changes to an electrical signal that travel through the optic nerve to the brain .the lens of the eye is attached to a ciliary muscle that can tighten or relax the lens making it thinner or fatter depending on how far away the objects are that a person is looking at. This allow the eye to focus the images sharply and clearly on the back of the retina.
what is electromagnetic radiation
a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.
What is wave motion
transfer of energy without matter
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refraction
is when light bends at a surface between two different substances.
why does refraction occur
light travels at different speeds through different substances the difference in speed results in different amounts of bending or refreaction
what is a lens
is a transparent piece of plastic or glass which is shaped to curve inwards and outwards
concave and convex
convex =out
concave=in
