Reflection

● Law of reflection -

when a light ray
strikes a reflecting
surface, the angle of
reflection equals the
angle of incidence

● Both angles are

measured from the
normal

Regular vs Diffuse Reflection

● If the beam of light falls on a smooth surface the rays

undergo regular reflection (parallel rays reflect parallel)

● If the beam of light falls on a rough surface, the rays

undergo diffuse reflection (parallel rays do not reflect
parallel)

Why is it harder to see when driving at

night after it has rained?

● Answer:

● Because the wet road is a smooth surface

and very little light is reflected back to our eyes

Are the pages of your book smooth

or rough?

● Answer:

● They are rough

● If they were smooth, there would be a lot

more glare and it would be harder to read.

Refraction

●
Refraction- the change in
speed and direction of light at
the boundary between 2 media.

●
Snells Law: ni sin øi = nr sin ør

●
When light travels from a less
optically dense medium into a
more optically dense medium,
the speed is reduced and the
angle of refraction is smaller
than the angle of incidence.

●
V= c/ nr

●
V = velocity

●
c = speed of light (3 E 8 m/s)

●
nr = index of refraction

​Snells Law: ni sin øi = nr sin ør

ni= index of refraction for incidence
nr= index of refraction for refraction
øi= angle of incidence
ør= angle of refraction

Snell's Law

Dispersion - separation of light into

the spectrum of colors

● Red light travels

fastest; it bends the
least; has the smallest index of refraction

● Violet light travels the

slowest, it bends the
most; has the largest index of refraction

Rainbows

● A rainbow is formed when sunlight is dispersed

by water droplets.

● This is a result of both reflection and refraction

Total internal reflection occurs when light passes from a more optically dense medium to a
less optically dense medium at such an angle that the angle of
refraction is 90 degrees.


Critical angle - angle of incidence that causes total internal reflection or the refracted angle to be 90 degrees

Critical Angle = sin^-1(1/n)

​Total Internal Reflection

All Finished!

​That's the notes for the chapter.

We will practice some Snell's Law and the other math together soon. I hope you have a good day and that you learned something in class.
Catch you on the flipside
-Coach Bush