2.7 Photons

Question 1

Light behaves like both a … and a …

Answer 1

Wave
Particle

Question 2

Electronvolt (eV)

Answer 2

Is the energy of an electron accelerated by a potential difference of 1 volt

Question 3

Which wavelengths is the visible spectrum between?

Answer 3

400nm and 700nm

Question 4

What is the typical wavelength for gamma rays?

Answer 4

10^-12

Question 5

What is the typical wavelength for X-rays?

Answer 5

10^-10

Question 6

What is the typical wavelength for UV waves?

Answer 6

10^-7 or 10^-8

Question 7

What is the typical wavelength for infra red waves?

Answer 7

10^-5

Question 8

What is the typical wavelength for Microwaves?

Answer 8

10^-2

Question 9

What is the typical wavelength for Radio waves?

Answer 9

10²

Question 10

What are the five steps in a photoelectric effect experiment?

Answer 10

1. Clean a zinc plate with steel wool
2. Attach the plate to the top disc on a gold leaf electroscope
3. Charge the zinc plate and inner assembly of the electroscope negatively (the gold leaf should now rise)
4. Place a UV lamp near the zinc plate (the gold leaf should now fall)
5. Repeat but with a positive charge in step 3

Question 11

Photoelectric effect

Answer 11

When light or ultraviolet radiation of short enough wavelength falls on a surface, electrons are emitted from the surface.

Question 12

Work function, Φ

Answer 12

The work function of a surface is the minimum energy needed to remove an electron from the surface

Question 13

What are the units for work function?

Answer 13

J or eV

Question 14

The remaining energy left over after work function has been lost is known as:

Answer 14

E_{k max}

Question 15

Threshold frequency, f₀

Answer 15

Is the minimum frequency of a photon that will cause the emission of an electron from a particular metal surface

Question 16

What is the equation for E_{k max} ?

Answer 16

E_{k max} = hf - Φ
h = planks constant
f = frequency

Question 17

Stopping voltage(eV_s) is equal to …

Answer 17

E_{k max}

Question 18

Ionisation energy

Answer 18

The ionisation energy of an atom is the minimum energy needed to remove an electron from the atom in its ground state

Question 19

If an electron wants to move up and energy level it must …

Answer 19

Absorb a photon

Question 20

Absorption spectra

Answer 20

Is the normal visible spectra with certain wavelengths missing, this is due to electrons absorbing these photons.

Question 21

Emission spectrum

Answer 21

Is a black space with a few lines on it which are the specific wavelengths of the electrons when they fall to lower wave lengths

Question 22

Electron diffraction

Answer 22

Is the evidence that particles act in the same way as waves in some instances.

Question 23

What is the equation for momentum of light?

Answer 23

λ = h / p
λ = wavelength
h = planks constant
p = momentum