Electromagnetic Radiation & Quantum Phenomena

Question 1

Are Electromagnetic Waves Transverse Or Longitudinal?

Answer 1

Transverse

Question 2

What Phenomenon Can Be Used To Show That Light Behaves As A Particle?

Answer 2

Photoelectric Effect

Question 3

Describe The Photoelectric Effect?

Answer 3

• When Light Above A Certain Frequency Is Shone On Metal
• Electrons Are Released
• Released Electrons Are Called Photoelectrons

Question 4

What Is The Threshold Frequency?

Answer 4

The Minimum Frequency Of Light Required For An Electron To Be Emitted

Question 5

What Is The Equation For The Energy Of A Photon?

Answer 5

• E = h/f

* E = hc/(wavelength)

Question 6

Why Does A Photon Need A Minimum Frequency To Liberate An Electron?

Answer 6

• Energy Of Photon Is Determined By It’s Frequency
• Photon Energy Must Be Greater Than Work Function
• In Order For Electron To Be Emitted

Question 7

If A Photon Has A Frequency Higher Than The Threshold Frequency, What Would Occur?

Answer 7

Electron Will Be Liberated & Remaining Energy Is Kinetic Energy Of Electron

Question 8

If Light Is Incident On Metal & Photoelectric Emission Does Not Occur, What Is The Effect Of Increasing Light Intensity?

Answer 8

• NO EFFECT
• More Intensity = More Photons Incident On Metal Each Second
• However - Each Photon Still Carries Same Energy
• Therefore - Not Enough Energy To Liberate Electron

Question 9

What Is The Photoelectric Equation?

Answer 9

hf = (work function) + Ek(Max)

Question 10

Define Work Function?

Answer 10

The Energy Required By An Electron To Overcome The Metallic Bond Holding It In The Metal

Question 11

What Is An Electron Volt?

Answer 11

The Kinetic Energy Of An Electron That Has Been Accelerated From Rest Through A P.D Of 1V

Question 12

How Do You Convert eV to J?

Answer 12

• eV - J = X(1.6x10-19)

* J - eV = /(1.6x10-19)

Question 13

How Does A Fluorescent Tube Work?

Answer 13

• High P.D Applied Across Mercury Vapour Accelerates Fast Moving Free Electrons Which Collides With Mercury Atoms
• Mercury Electrons Excite & De-Excite - releases UV photon
• Phosphorus Coating Absorbs UV Photon - Excites It - De Excites It - Emits It As Visible Light

Question 14

What Can Be Used As Evidence For The Discrete Energy Levels In Atoms?

Answer 14

• Line Emission & Absorption Spectra
• Lines Appear At Discrete Points = Light Photon Of Specific Frequency/Wavelength Has Been Absorbed Or Emitted
• Shows Electrons Can Only Absorb Exact Energy To Be Excited To Next Discrete Level

Question 15

What Is Wave Particle Duality?

Answer 15

• All Particles Have Both Particle & Wave Properties
• Particle = photoelectric effect
• Wave = diffraction

Question 16

What Is The De Broglie Wavelength Equation?

Answer 16

Wavelength = h/mv

• (mv = momentum)