Physics - waves (mixed subjects) Flashcards
what is absorbtion
when waves are absorbed into the material, transferring the energy into the materials energy stores.
what is reflection
when waves bounce back from a surface.
what is transmission
when waves travel through a material.
what is optical density
how quickly light travels through a material.
what is the refractive index
a measure of optical density, the bigger the refractive index, the more optically dense a material is.
what are wavefronts
imaginary lines drawn on a ray diagram showing wavelength.
what are the two types of reflection
specular and diffuse
what is specular reflection
when a ray reflects off a smooth surface and show a clear image.
what is diffuse reflection
when a ray reflects off a rough surface and it scatters.
why do rays scatter off a rough surface
the normal for each ray is different and so the angle of reflection is different for each ray.
why do opaque objects appear opaque
they absorb most wavelengths of light and reflect the rest.
why does a green hat appear black through a red filter
because the hat absorbs all light wavelengths that do not correspond to the colour green.
what is a black body
an object that absorbs all of the EM radiation that hits it.
define intensity
power per unit area
what objects emit radiation
all objects
name three rules about convex lenses
1) a ray travelling parallel to the axis will refract through the lens and intercept the principal focus.
2) a ray travelling through the middle of the lense will not refract it will continue in a straight line.
3) a ray that intercepts the principal focus before the lens will refract through the lens and leave parallel to the axis.
how do you find the principal focus on concave lens
where it looks like all the emerging rays would meet diverge. you can trace the emerging rays to a single point using virtual rays.
what is the focal length
the distance between the centre of a lens and the principal focus
what are three rules about concave lenses
1) an incident ray travelling parallel to the axis will emerge in a straight line to the principal focus
2) an incident ray travelling through the middle of the lens will continue in a straight line.
3) an incident ray passing towards the far side principal focus will emerge parallel to the axis.
what is a “real image”
when light rays from a point on an object come together to form an image.
what is a “virtual image”
when light rays from a point on an object are diverging after they have left the lens.
what three things do you need to say to describe an image
how big it is compared to the object.
whether it is upright or inverted in relation to the object.
whether it is real or virtual.
what sort of images to convex lenses produce.
real or virtual
what sort of images to concave lenses produce
virtual
what happens to a ray that goes through the centre of a lens
nothing, it continues in a straight line.
what do convex lenses do to light
converge it
what do concave lenses do to light
diverge it
