A proton, initially at rest, is accelerated through a potential difference of 1500 V . A proton has charge + 1 . 60 × 10 - 19 C and mass 1 . 67 × 10 - 27 kg . Calculate its final kinetic energy in joules (J)

Since, the proton is accelerated from rest, so energy gained by the proton is equal to the work done on proton by potential difference. Work done is W = Q V = 1 . 6 × 10 - 19 × 1500 = 2 . 4 × 10 - 16 J Hence, its final kinetic energy is 2 . 4 × 10 - 16 J .

A proton, initially at rest, is accelerated through a potential difference of 1500 V . A proton has charge + 1 . 60 × 10 - 19 C and mass 1 . 67 × 10 - 27 kg . Calculate its final kinetic energy in joules (J)

Since, the proton is accelerated from rest, so energy gained by the proton is equal to the work done on proton by potential difference. Work done is W = Q V = 1 . 6 × 10 - 19 × 1500 = 2 . 4 × 10 - 16 J Hence, its final kinetic energy is 2 . 4 × 10 - 16 J .

Table shows the work functions of several different metals. Metal Work function Φ / J Work function Φ / e V Caesium 3 . 0 × 10 - 19 1 . 9 Calcium 4 . 3 × 10 - 19 2.7 Gold 7 . 8 × 10 - 19 4.9 Potassium 3 . 2 × 10 - 19 2.0 Zinc 6 . 9 × 10 - 19 4 . 3 State which metal requires the highest frequency of electromagnetic waves to release electrons.

The work function of a given metal can be defined as the minimum amount of energy which is required to pull out an electron from an atom. This energy is equal to the energy of the electron revolving around the nucleus. Energies that exceed the work function can cause the release of an electron from the metal. Since gold had the maximum value of work function, so it requires the highest frequency of electromagnetic waves to release electrons.

Table shows the work functions of several different metals. Metal Work function Φ / J Work function Φ / e V Caesium 3 . 0 × 10 - 19 1 . 9 Calcium 4 . 3 × 10 - 19 2 . 7 Gold 7 . 8 × 10 - 19 4 . 9 Potassium 3 . 2 × 10 - 19 2 . 0 Zinc 6 . 9 × 10 - 19 4 . 3 State which metal will release electrons when the lowest frequency of electromagnetic waves is incident on it?

The work function of a given metal can be defined as the minimum amount of energy which is required to pull out an electron from an atom. This energy is equal to the energy of the electron revolving around the nucleus. Energies that exceed the work function can cause the release of an electron from the metal. Since caesium had the minimum value of work function, so it requires the lowest frequency of electromagnetic waves to release electrons.

Table shows the work functions of several different metals. Metal Work function Φ / J Work function Φ / e V Caesium 3 . 0 × 10 - 19 1 . 9 Calcium 4 . 3 × 10 - 19 2 . 7 Gold 7 . 8 × 10 - 19 4 . 9 Potassium 3 . 2 × 10 - 19 2 . 0 Zinc 6 . 9 × 10 - 19 4 . 3 Calculate the threshold frequency for zinc.

Threshold frequency is the minimum frequency of the incident radiation below which photoelectric emission is not possible irrespective of the intensity of the incident radiation. Emitted electrons are called photoelectrons. For zinc, threshold frequency is f 0 = ϕ h = 6 . 9 × 10 - 19 6 . 63 × 10 - 34 = 1 . 04 × 10 15 ≈ 1 × 10 15 Hz

Table shows the work functions of several different metals. Metal Work function Φ / J Work function Φ / e V Caesium 3 . 0 × 10 - 19 1 . 9 Calcium 4 . 3 × 10 - 19 2 . 7 Gold 7 . 8 × 10 - 19 4 . 9 Potassium 3 . 2 × 10 - 19 2 . 0 Zinc 6 . 9 × 10 - 19 4 . 3 Calculate the threshold wavelength for potassium.

Threshold frequency is the minimum frequency of the incident radiation below which photoelectric emission is not possible irrespective of the intensity of the incident radiation. Emitted electrons are called photoelectrons. For potassium, threshold frequency is f 0 = ϕ h = 3 . 2 × 10 - 19 6 . 63 × 10 - 34 = 4 . 83 × 10 14 Hz . Since wavelength of light is inversely proportional to its frequency, the threshold wavelength is the maximum wavelength of the light for which the metal will emit electrons. So wavelength is λ 0 = c f 0 = 3 × 10 8 4 . 83 × 10 14 = = ≈ 620 nm .

EASY

AS and A Level

IMPORTANT

Earn 100

A proton, initially at rest, is accelerated through a potential difference of $1500 V$ . A proton has charge $+ 1.60 \times 10^{- 19} C$ and mass $1.67 \times 10^{- 27} kg$ .

Calculate its final kinetic energy in joules (J)

Important Questions on Quantum Physics

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Question>Q 8

A proton, initially at rest, is accelerated through a potential difference of $1500 V$ . A proton has charge $+ 1.60 \times 10^{- 19} C$ and mass $1.67 \times 10^{- 27} kg$ . Calculate its final speed.

MEDIUM

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Question>Q 9

In an experiment to determine the Planck constant $h$ , LEDs of different colours were used. The p.d. required to make each conduct was determined, and the wavelength of their light was taken from the manufacturer's catalogue. The results are shown in Table. For each LED, calculate the experimental value for hand, hence, determine an average value for the Planck constant.

Colour of LED	Wavelength / $10^{- 9} m$	Threshold voltage / $V$
Infrared	$910$	$1.35$
Red	$670$	$1.70$
Amber	$610$	$2.00$
Green	$560$	$2.30$

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 10

Photons of energies $1.0 eV, 2.0 eV & 3.0 eV$ strike a metal surface whose work function is $1.8 eV$ . State which of these photons could cause the release of an electron from the metal.

MEDIUM

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 10

Photons of energies $1.0 eV, 2.0 eV & 3.0 eV$ strike a metal surface whose work function is $1.8 eV$ .

Calculate the maximum kinetic energies of the electrons released in each case. Give your answers in e V and in J.

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 11

Table shows the work functions of several different metals.

Metal	Work function $Φ / J$	Work function $Φ / e V$
Caesium	$3.0 \times 10^{- 19}$	$1.9$
Calcium	$4.3 \times 10^{- 19}$	2.7
Gold	$7.8 \times 10^{- 19}$	4.9
Potassium	$3.2 \times 10^{- 19}$	2.0
Zinc	$6.9 \times 10^{- 19}$	$4.3$

State which metal requires the highest frequency of electromagnetic waves to release electrons.

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 11

Table shows the work functions of several different metals.

Metal	Work function $Φ / J$	Work function $Φ / e V$
Caesium	$3.0 \times 10^{- 19}$	$1.9$
Calcium	$4.3 \times 10^{- 19}$	$2.7$
Gold	$7.8 \times 10^{- 19}$	$4.9$
Potassium	$3.2 \times 10^{- 19}$	$2.0$
Zinc	$6.9 \times 10^{- 19}$	$4.3$

State which metal will release electrons when the lowest frequency of electromagnetic waves is incident on it?

EASY

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 11

Table shows the work functions of several different metals.

Metal	Work function $Φ / J$	Work function $Φ / e V$
Caesium	$3.0 \times 10^{- 19}$	$1.9$
Calcium	$4.3 \times 10^{- 19}$	$2.7$
Gold	$7.8 \times 10^{- 19}$	$4.9$
Potassium	$3.2 \times 10^{- 19}$	$2.0$
Zinc	$6.9 \times 10^{- 19}$	$4.3$

Calculate the threshold frequency for zinc.

MEDIUM

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 28 - Quantum Physics>Questions>Q 11

Table shows the work functions of several different metals.

Metal	Work function $Φ / J$	Work function $Φ / e V$
Caesium	$3.0 \times 10^{- 19}$	$1.9$
Calcium	$4.3 \times 10^{- 19}$	$2.7$
Gold	$7.8 \times 10^{- 19}$	$4.9$
Potassium	$3.2 \times 10^{- 19}$	$2.0$
Zinc	$6.9 \times 10^{- 19}$	$4.3$

Calculate the threshold wavelength for potassium.

A proton, initially at rest, is accelerated through a potential difference of 1500V. A proton has charge +1.60×10-19C and mass 1.67×10-27kg. Calculate its final kinetic energy in joules (J)

Important Questions on Quantum Physics

Learn and Prepare for any exam you want !

A proton, initially at rest, is accelerated through a potential difference of $1500 V$ . A proton has charge $+ 1.60 \times 10^{- 19} C$ and mass $1.67 \times 10^{- 27} kg$ .

Calculate its final kinetic energy in joules (J)