Chapter 7: Wave Nature of Light

Question 1

frequency (v)

Answer 1

cycles per second (s^-1 or Hz)

Question 2

wavelength

Answer 2

the distance a wave travels in one cycle

Question 3

amplitude

Answer 3

the depth of a trough or height of a wave crest

Question 4

speed (c) =

Answer 4

frequency x wavelength

Question 5

3.00 x 10^8 m/s in a vacuum

Answer 5

the speed of light, a constant
*Visible light is a type of electromagnetic radiation.described by the previous 3 variables (frequency, amplitude and wavelength)

Question 6

a wave with higher amplitude =

Answer 6

brighter

Question 7

a wave with lower amplitude =

Answer 7

dimmer

Question 8

1A =

Answer 8

10^-10 m

Question 9

s^-1

Answer 9

(inverse second) x/ PER second

Question 10

E=nhv

Answer 10

E= energy; n= a positive integer; h = Planck’s constant; (v = frequency)

Question 11

A solid object emits visible light when it is heated to about 1000K.

Answer 11

Blackbody radiation

Question 12

Color is related to wavelength and frequency, while temperature is related to energy

Answer 12

the color (and intensity) of the light changes as the temperature changes [E=nhv]

Question 13

1. Any object (including atoms) can emit or absorb on certain quantities of energy
2. Energy is quantized; it occurs in fixed quantities, rather than being continuous. Each fixed quantum of energy is called a ‘quantum’.
3. An atom changes its energy state by emitting or absorbing one or more quanta of energy
   (deltaE = nhv, where n can only be a whole #)

Answer 13

Quantum Theory of Energy

Question 14

E=hv = hc/wavelength

Answer 14

to find the energy of one photon

Question 15

(1/frequency) = R (1/n1^2 - 1/n2^2)
R = 1.096776x10^7 m^-1

Answer 15

the Rydberg equation; R = the Rydberg constant; for the visible series, n1 = 2, n2 = 3, 4, 5…

Question 16

an atom’s lowest energy state

Answer 16

the Ground State

Question 17

deltaE = E(final) - E(initial) =

to find the change in E of an atom that emits (Ef-Ei) or absorbs (Ei-Ef) a photon of light

Answer 17

= -2.18x10^-18J x [(1/n(final)^2) - (1/n(initial)^2)]

Question 18

wavelength = h/(m x u) 
or = Planck's constant/speed x mass

Answer 18

Calculating the de Broglie wavelength of an electron

Question 19

to find the wavelenght of a photon =

Answer 19

wavelength = hc/deltaE

= (Planck’s constant x speed)/change in energy of the atom

Question 20

ultraviolet–> (n=1) - (n=6)
visible–> (n=2) - (n=6)
infrared–> (n=3) - (n=6)

Answer 20

3 spectral lines emitted by the H atom

Question 21

[E = mc^2]

Matter and energy are alternate forms of the same entity
All matter exibits properties of both particles and waves; electrons have wave-like motion and, therefore, have only certain allowable frequencies and energies
Matter behaves as if it moves in a wave*

Answer 21

the Wave Particle Duality of Energy and Matter

*the de Broglie wavelength for any particle is given by:
[wavelength = h/mU]
(m= mass and U = speed in meters/second)

Question 22

6.626x10^-34 J (or kg x m^2/s)

Answer 22

Planck’s constant

Question 23

Classical Theory:
*Matter is particulate and massive
*Energy is continuousand wavelike
led to…

Answer 23

*Since matter is discontinuous and particulate…
perhaps energy is also discontinuous and particulate
*Since energy is wavelike, perhaps…
matter is wavelike
*Since matter has mass, perhaps…
energy has mass

Question 24

*Since matter is discontinuous and particulate…
perhaps energy is also discontinuous and particulate–
Observation: Blackbody radiation

Answer 24

Planck’s theory: Energy is quantized–only certain values allowed

Question 25

*Since matter is discontinuous and particulate…
perhaps energy is also discontinuous and particulate–
Observation: Photoelectric effect

Answer 25

Einsteins’s theory:

light has particulate behavior (photons)

Question 26

*Since matter is discontinuous and particulate…
perhaps energy is also discontinuous and particulate–
Observation: Atomic line spectra
Bohr’s theory:

Answer 26

energy of atoms is quantized; a photon emitted when electron changes orbit

Question 27

*Since energy is wavelike, perhaps…
matter is wavelike–
Observation: (Davisson/Germer)-
electron beam is diffracted by metal crystal

Answer 27

de Broglie’s theory:

All matter travels in waves; energy of atom is quantized due to wave motion of electrons

Question 28

*Since matter has mass, perhaps…
energy has mass
Observation: (Compton)
Photon’s wavelength increases (and momentum decreases) after colliding with an electron

Answer 28

Enstein/de Broglie theory:

mass and energy are equivalent; particles have wavelength and photons have momentum

Question 29

It is not possible to know both the position and the momentum of a moving particle at the same time;

[change in position * mass * change in speed is greater than or equal to (Planck’s constant/4 * pi)]

The more accurately we know the speed, the less accurately we know the position, and vice versa

Answer 29

Heisenberg’s Uncertainty Principle:

[delta x * mass * delta U >/= (h/4pi)]

Question 30

9.11 x 10^-31 kg

Answer 30

the mass of an electron

Question 31

The hydrogen atom has only certain energy levels, which Bohr called ‘stationary states’:

Answer 31

Bohr’s atomic model

Question 32

Each state is associated with a fixed circular orbit of the electron around the nucleus

Answer 32

(Bohr’s atomic model)

Question 33

the higher the energy level, the farther the orbit is from the nucleus

Answer 33

(Bohr’s atomic model)

Question 34

when the H electron is in the first orbit, the atom is in its lowest energy state–the ‘ground state’

Answer 34

(Bohr’s atomic model)

Question 35

*The atom doesn’t radiate energy while in one of its stationary states

Answer 35

(Bohr’s atomic model)

Question 36

*The atom changes to another stationary state only by emitting or absorbing a photon

Answer 36

(Bohr’s atomic model)

Question 37

the energy of the photon (hv) equals the difference between the energies of the two energy states

Answer 37

(Bohr’s atomic model)

Question 38

when the E electron is in any energy state higher than n=1, the atom is in an excited state

Answer 38

(Bohr’s atomic model)