1. Unit 11 – Modern Physics

3. _______________physics
Matter is a____________________
Light is a _________________.
Classical
particle
wave
This is "everyday" physics that deals with objects
that are relatively
1. _____________  bigger than _____________
2. _____________  v << _____
large
atoms
slow c
_______________ modified classical physics so that
it would give more accurate results when speeds
_______________________________ and for________________.
His theories are called the ________________ and
________________ Theories of _________________________ .
Einstein
were close to c
gravity
Special
General
Relativity

5. _______________ physics modified physics to deal with
_________________________ on the scale of ___________ .
According to this theory:
Matter can act like a___________________________.
Light can act like a___________________________.
Modern
tiny objects
atoms
particle or a wave
particle or a wave
Ex: Light in the classical view acts like a ___________
whose _________________ determines its energy:
wave
amplitude
_______________
 more____________
brighter
energy

6. Ex: The ___________________ effect showed that light
can act like a ______________________ .
photoelectric
particle
shine
light
electrons e-
“photo…”
“…electric”
zinc
color of light
brightness
of light
how many electrons were ejected
from the zinc and with what KE
red
dim
no e-
bright
violet
a few e- with lots of KE
lots of e- with lots of KE

7. Duality:
wave
particle

8. Einstein _____________________________ for a paper that
explained the photoelectric effect by assuming light
acted like ______________. The higher its _______________
the greater the energy of the light particle. Bright light
consists of ___________ particles.
won a Nobel Prize
particle
frequency
many
dim red
_______________ light:
low
 1_______ energy particle
cannot eject an e-
none of these many
_______ energy particles
could eject an e-
low
________________light:
bright red
dim violet
high
________________light:
 1_______ energy particle
can eject 1 e-
each of these many
________ energy particles
could eject an e-
high
bright violet
________________light:

9. The ______________ (basic unit) of electromagnetic
energy (light) is called a _______________ . It has no
mass, but carries ______________ and ________________ .
Its energy is given by:
quantum
photon
energy
momentum
Eph =
where h = =
Ex: What is the
relationship between
Eph and f?
Eph f
What quantity does the slope of the line?

10. See page 1 of Reference Tables

11. Page 1:
top

12. The ______________ (basic unit) of electromagnetic
energy (light) is called a _______________ . It has no
mass, but carries ______________ and ________________ .
Its energy is given by:
quantum
photon
energy
momentum
Eph = hf
where h = =
Planck's constant
6.63 x J·s
Ex: What is the
relationship between
Eph and f?
Eph f
What quantity does the slope of the line?
Eph/f = ? h

14. Ex: What is the relationship between Eph and l?
Start with the equation:
Substitute c in for v:
Solve for f:
Substitute in the equation for
v = fl
c = fl
f = c/ l
Eph= hf
Eph= hc/l
Ex: What is the
relationship between
Eph and l in graph form?
Eph l
The greater the wavelength, the ___________ the energy.

16. Ex: What is the relationship between Eph and l?
Start with the equation:
Substitute c in for v:
Solve for f:
Substitute in the equation for
v = fl
c = fl
f = c/ l
Eph= hf
Eph= hc/l
Ex: What is the
relationship between
Eph and l in graph form?
Eph l
The greater the wavelength, the ___________ the energy.
less

17. Ex: Find the energy of a blue light photon in joules.
Eph = hf = hc/l
= (6.63 x J·s) (???)
Convert the answer to electronvolts (eV).
page 1 of RT: eV = ________________ J

18. Choose f = 6.5 x 1014 Hz

19. Ex: Find the energy of a blue light photon in joules.
Eph = hf = hc/l
= (6.63 x J·s)
(6.5 x 1014 Hz)
= 4.3 x J
Convert the answer to electronvolts (eV).
page 1 of RT: eV = ________________ J

20. Page 1:
top

21. Ex: Find the energy of a blue light photon in joules.
Eph = hf = hc/l
= (6.63 x J·s)
(6.5 x 1014 Hz)
= 4.3 x J
Convert the answer to electronvolts (eV).
1.6 x 10-19
See page 1 of RT: eV = ________________ J
Eph = 4.3 x J x
_______1 eV_______
1.6 x J
Eph = 2.7 eV

22. _____________ theory - ____________________ energy
is emitted from and absorbed by _______________
in _____________ amounts or ________________ .
( ______________ means "separate, individual pieces.")
Quantum
electromagnetic
matter
discrete
"packets"
Discrete
Ex: _______________
of a photon
absorption
before:
after:
atom has
______ energy
atom
more
emission
Ex: _____________
of a photon
before:
after:
atom has
_______ energy
atom
less

23. Ex The ____________Effect: X-rays scatter off electrons.
Compton
e- at rest  KE =____
v=c
before
collision:
_______
photon
x-ray
now has KE
e- ____________
after
collision:
The scattered
photon now has
_______ energy.
So its f is _______
and its l is
______________
less
less c
longer
momentum
energy
Both _________________and ______________ are conserved.

24. In sum, light can act like a __________________ or like
a ____________ . Which one it acts like depends on
the situation. When light interacts with..
particle
wave
… __________ , it acts
like a _________________
Examples:
1/ __________________
2/ __________________
light
… ___________ , it acts
like a __________________
Examples:
1/ __________________
2/ __________________
3/ __________________
atoms
wave
particle
interference
absorption
diffraction
emission
collisions
Even when it is described as a photon, we still
use __________ properties such as _______________
and _________________ to describe it.
wave
frequency
wavelength

25. Electron charge: In 1909, Millikan sprayed drops of
________ into an _______________ field E.
oil
electric
Fe =___ qE
oil drop
Fg =_____ mg
By suspending the oil drop then letting it fall,
he was able to discover that the oil drops always carried
an ___________________________ of the fundamental charge
= ______________________ (the ______________ of charge).
which is the charge on 1 _____________ or _____________ .
 Charge is __________________ .
integer multiple
1.6 x C
quantum
proton
electron
quantized