An incident ray from air strikes dolomite (n = 2.0) at an angle of 30o from normal.

Calculate: refl & refr

Chapter 19Diffraction & Interference

List & describe 3 properties of

waves

Diffraction•The bending of light rays when passing a barrier

Diffraction•Named by Francesco

Grimaldi by seeing blurred edges of

shadows

Isaac Newton•Predicted that light moved in the form of particles to explain

diffraction

Christiaan Huygens•Predicted that light moved in the form of

waves to explain diffraction

Thomas Young•Proved that light moved in the form of waves by

passing light thru a double slit. P 445

Thomas Young•The interference pattern caused by

diffraction produced dark & light lines

Monochromatic Light

•Light having only one wavelength

Coherent Waves

•Waves all in the same phase

Diffraction Interference

Lightwaves

d

n

n

L

x

x L d

=

Diffraction Interference

x L d

=

xd L

=Double

slit

Calculate wavelength reinforced when waves passing through 2 slits 25 m apart cast bright lines 4.0 cm apart on a

screen 2.0 m away

Calculate wavelength reinforced when waves

passing through 2 slits 25 m apart cast bright lines

that make a 37o angle from the principle axis

Diffraction Interference

d = distance between slits

w = slit width

xd xw L L

= =

Diffraction Interference

Lightwaves

d

n

n

L

x

d sin

Wave Properties• Propagation• Reflection• Refraction• Diffraction • Interference

Propagation•Within a uniformed

medium, the generation of waves that move in straight

lines called rays

Reflection•The bouncing of

waves off surfaces or medium boundaries

Refraction•The bending of

waves when passing from one medium to

another

Diffraction•The bending of

waves when passing around barriers

Interference•The superimposing two or more waves passing through the

same medium simultaneously

Photoelectric Effect•The emission of

electrons (e-)from a substance when

irradiated

1st Law of Ph Eff•The rate of e- emission

is proportional to the intensity of the incident

light

2nd Law of Ph Eff•The KE of e- emission

is independent of the intensity of the incident

light

Photoelectric Effect•This led to the

discovery that e- in atoms exist in

distinct energy levels

Spectroscopy•The study of a substance under

continuous excitation energy

Energy of a Wave

Ewave = hf

Energy of Matter

Ematter = mc2

Duality of Nature

Proposed by Louis de Broglie

Duality of NatureAll energy transfer exhibits properties of both waves &

particles

Duality Formula

= hmv

Calculate the wavelength 2.21

kg of a ball thrown at 20.0 m/s

Calculate the mass of blue light at

442 nm

Calculate the wavelength of a 442 Mg truck moving at 36

km/hr

Calculate the wavelength of a 4.42 x 106 Mg

train moving at 72 km/hr

The of near IR red light is 663 nm.Calculate: E & m of

the light

The of near UV light is 221 nm.

Calculate: E & m of the light

Calculate wavelength reinforced when waves

passing through 2 slits 25 m apart cast bright lines

that make a 53o angle from the principle axis

Calculate wavelength reinforced when waves

passing through a slit 75 m slit cast bright lines

that make a 53o angle from the principle axis

Calculate wavelength reinforced when waves passing through 2 slits 75 m apart cast bright lines 5.0 cm apart on a

screen 2.5 m away

Calculate wavelength reinforced when waves

passing through a 15 m slit cast bright lines 3.0 cm apart on a screen 2.5

m away

A wavelength 180 nm is reinforced when waves

passing through a 15 m slit cast bright lines 3.0 cm apart. What is the

screen distance?

A wavelength 18 nm is reinforced when waves passing through a 1.5

m slit cast bright lines 3.0 cm apart. What is the

screen distance?

Review

Calculate wavelength reinforced when waves

passing through a 25 m slit cast bright lines 5.0

cm apart on a screen2.5 m away

Calculate the mass & energy of UV light at

221 nm.

Calculate Kinetic energy &

wavelength of a 442 g ball going

30.0 m/s

Calculate wavelength reinforced when waves

passing through a slit 4.5 m slit cast bright lines

that make a 37o angle from the principle axis