Quantum

Question 1

when an electron collides with an atom and the electron is excited, what happens to the excess energy of the incident electron

Answer 1

Converted to kinetic energy of the incident electron after the collision

Question 2

Explain how mercury atoms are excited and de-excited

Answer 2

• Electrons collide with mercury atoms, causing them to transfer energy to the electrons. If the orbital electrons gain enough energy, they will excite to a higher energy level
• The excited electrons de-excite back to the ground state, emitting a photon of EQUAL energy to the energy difference between the levels

Question 3

How are visible light photons emitted from the fluorescent tube.

Answer 3

The phosphorus coating absorbs the UV photons, which causes orbital electrons to gain enough enough to excite to a higher energy level.

The orbital electrons de excite, which emits photons, which has energy equal to the energy difference between levels.

This difference is smaller than that for the mercury atoms, meaning the photons have lower energy, so lower wavelength so are in the visible light range

Question 4

Describe how photoelectric effect occurs

Answer 4

• PHOTONS OF LIGHT incident on metal surface causes electrons ON THE SURFACE OF THE METAL to be emitted

Question 5

Why is hf - work function the maximum value of KE

Answer 5

Because work function is the minimum energy required for photoelectric emission. Electrons deeper in the metal require more

Question 6

What is intensity of photons

Answer 6

number of photons emitted per second

Question 7

state and explain what material should be used as a grating for electron diffraction

Answer 7

Crystal/graphite sheet as the spacing between the atoms needs to be similar to the wavelength of electrons

Question 8

define ionisation energy

Answer 8

minimum energy transferred to an orbital electron required for it to leave the atom entirely FROM THE GROUND STATE

Question 9

How does the photoelectric effect suggest the existence of photons

Answer 9

• There is a threshold frequency/work function so wave theory is wrong
• Intensity doesn’t affect KE but a waves intensity is proportional to energy so wave theory must be wrong

Question 10

What determines a waves ability to penetrate a material

Answer 10

Its energy exerted on the material