CEM 141 Exam 2 Questions With Correct Answers

CEM 141 Exam 2 Questions With Correct
Answers
To |understand |atomic |structure |we |need |to |understand |electromagnetic |radiation. |- |CORRECT |
ANSWER✔✔-What |is |electromagnetic |radiation?

What |are |some |examples |that |you |encounter?



Examples |of |electromagnetic |radiation |- |CORRECT |ANSWER✔✔-•Radio |waves

•Microwaves

•Infrared

•Visible

•Ultraviolet

•X-rays

•Gamma |rays



How |do |we |characterize |electromagnetic |radiation? |What |is |different |about |radio |waves |and |
X-rays?



Two |models |are |used |to |describe |the |behavior |or |light |(electromagnetic |radiation). |What |is |
light? |- |CORRECT |ANSWER✔✔-A |wave |and |a |particle



Electromagnetic |radiation |- |CORRECT |ANSWER✔✔-•Wavelength, |λ |(m) |- |distance |from |peak |to
|peak



•Frequency, |v |(Hz=1/s) |- |number |of |wave |fronts |per |sec

•c=λ |x |v

-Where |c=velocity |of |light |(3.00 |x |10^8 |m |(1/s))

•Amplitude |- |height |of |peaks |(intensity)

,•Energy |- |increases |as |frequency |increases |(and |wavelength |decreases)



The |Electromagnetic |Spectrum |- |CORRECT |ANSWER✔✔-Note: |Scale |on |the |Spectrum |is |a |log |
Scale



•Lets |say |we |have |2 |objects |1 |m |apart |(10^0 |m)...

•How |far |apart |would |2 |objects |be |that |were |10^1 |m |apart?

-10 |m

•How |far |apart |would |2 |objects |be |that |were |10^2 |m |apart?

-100 |m

•How |far |apart |would |2 |objects |be |that |were |10^3 |m |apart?

-1000 |m



Relative |Wavelength |Sizes |- |CORRECT |ANSWER✔✔-



1 |nm |- |CORRECT |ANSWER✔✔-1 |x |10^-9 |m



Properties |of |Wave |Diffraction |- |CORRECT |ANSWER✔✔-



Properties |of |Wave |Interference |- |CORRECT |ANSWER✔✔-



Properties |of |Waves: |Diffraction |Patterns |- |CORRECT |ANSWER✔✔-



Which |has |longest |wavelength?

A. |X-rays

B. |Visible

,C. |Infrared |- |CORRECT |ANSWER✔✔-C. |Infrared



Which |has |highest |frequency?

A. |X-rays

B. |Visible

C. |Infrared |- |CORRECT |ANSWER✔✔-A. |X-rays



Which |has |highest |energy?

A. |X-rays

B. |Visible

C. |Infrared |- |CORRECT |ANSWER✔✔-A. |X-rays



Scale:

Which |EM |radiation |has |wavelengths |on |the |order |of |the |sizes |of |atoms?

A. |Radiowaves |(λ |~ |m)

B. |Microwaves(λ |~ |cm)

C. |X-rays |(λ |~ |nm)

D. |Gamma |rays |(λ |~ |1 |x |10^-16 |m) |- |CORRECT |ANSWER✔✔-C. |X-rays |(λ |~ |nm)



Energy |of |Light |- |CORRECT |ANSWER✔✔-•Short |wavelengths |(and |high |frequency) |EM |
radiation |"higher |in |energy"

•How |to |explain |this |with |the |wave |model?



So |— |light |is |a |wave?

With |a |frequency, |a |wavelength |and |speed? |- |CORRECT |ANSWER✔✔-Problem: |Wave |nature |of
|light |does |not |explain |some |phenomena.

, Photoelectric |Effect |Description |- |CORRECT |ANSWER✔✔-•Many |metals |emit |electrons |when |
electromagnetic |radiation |shines |on |the |surface

•The |light |is |transferring |energy |to |the |electrons |at |the |metal |surface |- |where |it |is |
transformed |into |kinetic |energy |that |give |the |electrons |enough |energy |to |"leave" |the |atoms |in
|the |metal



•Uses |- |photomultipliers, |photocells, |garage |door |openers



Why |does |adding |energy |in |the |form |of |light |(EM |radiation) |allow |electrons |to |"escape"? |- |
CORRECT |ANSWER✔✔-What |is |keeping |them |on |the |atoms?



The |photoelectric |effect |- |CORRECT |ANSWER✔✔-



Predict |what |happens |when:

1. |You |increase |the |intensity |of |UV |light

A. |Number |of |electrons |emitted |increases

B. |Number |of |electrons |emitted |decreases

C. |Nothing

D. |No |more |electrons |emitted |- |CORRECT |ANSWER✔✔-A. |Number |of |electrons |emitted |
increases



Predict |what |happens |when:

2. |You |keep |the |intensity |the |same |and |increase |the |wavelength |(decreasing |the |frequency) |
into |the |violet

A. |Number |of |electrons |emitted |increases

B. |Number |of |electrons |emitted |decreases

C. |Nothing

D. |No |more |electrons |emitted |- |CORRECT |ANSWER✔✔-C. |Nothing