Unit 1: Light

Question 1

Light: Relation to atom

Answer 1

No electron behaviour from nuclear model

●Comes from interaction w/ light

●Relates to electrons

●Light interaction = clues

Question 2

emission spectra

Answer 2

the wavelengths of light emitted from an electronically excited atom

Question 3

Electromagnetic radiation

Answer 3

Wave behavior

Question 4

wavelength (m)

Answer 4

the distance peak to peak or trough to trough in a wave

Question 5

Frequency (Hz)

Answer 5

the number of wavelengths per unit time

Question 6

Continuous spectrum

Answer 6

a spectrum that consists of a continuum (unbroken) of wavelengths.

Question 7

Light

Answer 7

Energy, not matter

●Travels at 3.0x108 m/s.
●Alternating magnetic/electric waves
●Speed = wavelength x frequency
●c = λ x ν

Question 8

Light

Answer 8

1x106 to 1x10-16 m

Question 9

Energy

Answer 9

c= ν x λ

●Can calculate frequency or wavelength

●Given light of frequency 2.73x1016 s-1 (UV), calculate the wavelength of the light

●Visible/UV are small wavelengths

●Usually nm (10-9 m) or a unit called angstroms (Å, 10-10 m)

Question 10

Photoelectric effect

Answer 10

light shining on a clean metal surface causes electrons to be ejected from the surface.

●Demonstrates particle
●Minimum energy, but based on intensity

●Einstein et. al particle behaviour

Question 11

Particle Behavior:

Photon

Answer 11

Photon – term referring to the particulate aspect of light

Question 12

Particle behavior:

quantum

Answer 12

a single “packet” or fixed amount of light energy

Question 13

Particle Behavior

Answer 13

Energy is determined using Planck’s constant h in the equation E = hν

●Planck’s constant: 6.626x10-34 J∙s

Question 14

Calculate the energy of light of frequency 2.73x1016 s-1 and wavelength 5.70x10-7 m

Answer 14

Lol

Question 15

Spectra

Answer 15

Atoms have characteristic light spectrum associated with interactions
●emission spectrum – the wavelengths of light emitted from an electronically excited atom

●absorption spectrum – the wavelengths of light absorbed in electronically exciting an atom

●Spectra are like fingerprint of atom

Question 16

Emission spectra of an element includes green line of 4.86x10-7 m – calculate energy of one photon

Answer 16

Lol

Question 17

Rydberg Equation

Answer 17

Johann Balmer/Johannes Ryberg related wavelength to electronic transition

●Rydberg constant – 1.097x107 m-1

●Rydberg equation: 1/λ = R(1/n12 – 1/n22)

Question 18

Example

Answer 18

Lol

Question 19

Bohr Model

Answer 19

●Niels Bohr – determine location from nucleus and stability

●Atomic radius, potential energy

●Electrons only in “allowed” states

●Developed quantization model

• “excited state” from “ground state”
• “promoted” to higher n.
• “relaxes” back to lower n.
• Releases photon w/ energy from n difference

Question 20

Calculate the wavelength and energy of light of frequency 4.83x1017 s-1 ; what energy is a photon of this wavelength?

●What wavelength is expressed in the transition n1 = 1 to n2 = 4?

Answer 20

Lol