M4C5

Question 1

Define a quantum

Answer 1

A small package of energy

Question 2

Define quanta

Answer 2

The number of small packets of energy

Question 3

Define photon

Answer 3

The quantum associated with electromagnetic radiation

Question 4

What is the value of Planck’s constant?

Answer 4

6.626x10^-34 J s

Question 5

What is the equation for working out the energy of a single photon?

Answer 5

E = hf
E = energy (J)
h = Planck's constant (6.626x10^-34 J s)
f = frequency (Hz or s^-1)

Question 6

What is the equation for working out the energy of a group of photons?

Answer 6

E = nhf
E = energy (J)
n = a whole number that indicate the number of quantum
h = Planck's constant (6.626x10^-34 J s)
f = frequency (Hz or s^-1)

Question 7

What is the equation for working out the energy of a single photon, when you substitute out f?

Answer 7

E = hc/λ
E = energy (J)
h = Planck's constant (6.626x10^-34 J s)
c = the speed of light (3.0x10^8 m s^-1)
λ = wavelength (m)

Question 8

What is an electronvolt (eV)?

Answer 8

A unit invented to be used in place of joules when dealing with photons because it would otherwise be really small
1 eV = 1.6x10^-19 J

Question 9

Define electronvolt

Answer 9

The kinetic energy gained by an electron when it’s accelerated through a potential difference of 1 volt

Question 10

What is the photoelectric effect?

Answer 10

The idea that when light of a certain frequency is shone onto a piece of metal it will begin to release electrons (the released electrons are called photo electrons)

Question 11

Define threshold frequency

Answer 11

The lowest possible frequency of light that will result in the emission of electrons from a particular metal. For most metal, this frequency is in the ultraviolet region of the electromagnetic spectrum.

Question 12

Define work function φ

Answer 12

The minimum energy required to release an electron from its surface, overcoming the electrostatic attraction between the electron and the positive metal ions.

Question 13

What is the photoelectric effect equation?

Answer 13

hf = φ + KEmax
h = Planck's constant (6.626x10^-34 J s)
f = frequency (Hz or s^-1)
φ = work function of the metal (J or eV)
KEmax = maximum possible kinetic energy of an emitted photoelectron (J or eV)

Question 14

Define stopping potential

Answer 14

The potential necessary to stop any electron from ‘reaching the other side’ of a photocell.

Question 15

What is the stopping potential equation?

Answer 15

eV = KEmax 
e = charge on an electron 1.6x10-19 C
V = stopping potential (V)
KEmax = maximum photoelectron kinetic energy (J or eV)

Question 16

How would you plot the stopping potential equation on a graph

Answer 16

eV = KEmax
KEmax = hf - φ
V = (h/e)f - φ/e
This looks like….
y = mx + c

Question 17

What is the equation to work out the wave length of a particle?

Answer 17

λ = h/mv
p = mv
λ = h/p
λ = wavelength (m)
h = Planck's constant (6.626x10^-34)
m = mass (kg)
v = velocity (m s^-1)
p = momentum (kg m s^-1)

Question 18

What is the equation to work out the wave length of a particle? Using eV

Answer 18

λ = h / √(2mVe)
λ = wavelength (m)
h = 6.626x10-34 J s
m = mass (kg)
V = accelerating potential difference (V)
e = charge on one electron (1.6x10-19 C)