Ch 17 Notes

1. Ch 17
Reflection and Refraction

2. Reflection
 Law of reflection -
when a light ray
strikes a reflecting
surface, the angle of
reflection equals the
angle of incidence

3. 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)

4. 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

5. 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.

6. 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

7. 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.
 Crtitical angle - angle of
incidence that causes
total internal reflection

8. 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

9. Rainbows
 A rainbow is formed when sunlight is dispersed
by water droplets.