reflection and refraction

reflection definition

bouncing back of a wave to original medium whne it meets a surface or boundary that it cannot pass through.

law of reflection

angle of incidence is equal to the angle of reflection. incident ray, the normal to the mirror at the point of incidence and reflected rays lie on the same plane.

incident ray

ray of light that strikes a surface

reflected ray

ray of light tha tbounces off a surface

normal

imaginery line drawn perpendicular to the surface

angle of incidence

angle between incident ray and the normal

angle of reflection

angle between reflected ray and the normal

refraction

refraction is the bending of a wave when it passes from one medium to another. it occurs due to changes of the speed of waves

refractive index

n= speed of light in vacuum / speed of light in medium

refractive index for air, vacuum, water

n=1.003, n=1, n=1.33

snells law

n1sintheta1 = n2sintheta2

rules of refraction

when light passes from less dense to denser. slows down bends toward normal

when light passes from denser to less dense. speeds up bends away from normal

total internal reflection

Occurs when a light ray traveling from a denser medium to a rarer medium is completely reflected back into the denser medium. only occurs when the angle of incidence is greater than the critical angle.

critical angle

angle of incidence in the denser medium for which the angle of refraction in the less dense medium is 90°

critical angle formula

n=1/sinc

dispersion of light by prisim

splitting of white light into its spectrum when it passes through a prisim. different wavelengths of light refracts by different amounts

diffraction

spreading out of waves when they pass through a narrow opening or move around an obstacle. depends on the relationship between wavelength and the size of gap

gap is greater than wavelength

little spreading

gap=wavelength

strong diffraction

wavelength greater than gap

waves spread out significantly

interference

interference occurs when 2 or more waves overlap and their amplitudes combine either reinforcing or cancelling each toher

constructive

when 2 waves meet in phase. results in a larger amplitude.

destructive interference

when 2 waves meet out of pahse resulting in waves canceling or become smaller