Ceist Eile

Ceist Eile is in development. Features, questions and prices may change while we refine it.

Subjects · Leaving Cert Physics

Leaving Cert Physics: The photoelectric effect

How often The photoelectric effect comes up on the Physics papers, every year it was asked, and questions to try.

HL Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 7 of the last 10 Ordinary Level papers, most recently in 2026. most years

June 2027 is the first exam on the new Physics course. These come from the 2016–2026 papers, so read them as a guide.

The photoelectric effect, Higher Level(7 marks)

Quick ones on The photoelectric effect.

(a)Formula for the energy of a photon?
  1. E = h/f
  2. E = hf
  3. E = hλ
(b)Energy of a photon of frequency 5.0 × 10¹⁴ Hz (h = 6.6 × 10⁻³⁴ J s)?
  1. 1.3 × 10⁻¹⁸ J
  2. 3.3 × 10⁻²⁰ J
  3. 3.3 × 10⁻¹⁹ J
(c)Einstein's photoelectric equation?
  1. hf = Φ + ½mv²max
  2. Φ = hf + ½mv²max
  3. hf = Φ − ½mv²max
Show the answers

(a) E = hf

(b) 3.3 × 10⁻¹⁹ J

(c) hf = Φ + ½mv²max

Your turn: Higher Level questions on The photoelectric effect.

Higher Level

Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q6(k)
2025Q9
2024Q6(k)
2023Q14(d)
2022Q14(c)
2021Q14(c)
2019Q8
2018Q12(d)
2017Q10
2016Q5(h), Q11

Links open the State Examinations Commission’s paper for that year.

More The photoelectric effect questions

The photoelectric effect, 3 marks

Define the photoelectric effect.

  1. The emission of light from a metal surface when it is heated to a high temperature
  2. The emission of electrons from a metal filament when it is heated to a high temperature
  3. The emission of electrons from a metal surface when light of a high enough frequency falls on it
Show the answer

The emission of electrons from a metal surface when light of a high enough frequency falls on it

Below the threshold frequency no electrons are emitted, no matter how bright the light. That is why light must be treated as photons of energy hf.

The photoelectric effect, 3 marks

What is the threshold frequency of a metal?

  1. The frequency of light at which the photocurrent is greatest
  2. The minimum frequency of light that will eject electrons from that metal
  3. The maximum frequency of light that the metal surface can absorb
Show the answer

The minimum frequency of light that will eject electrons from that metal

Below it no electrons are emitted however bright the light, because each photon carries too little energy, that is hf is less than the work function.

The photoelectric effect, 3 marks

In the photoelectric effect, why does brighter light not give the electrons more kinetic energy?

  1. Each electron absorbs one photon, whose energy depends only on the frequency
  2. Brighter light has a lower frequency, so each photon carries less energy
  3. The extra energy is shared out among many more electrons, so each gets the same
Show the answer

Each electron absorbs one photon, whose energy depends only on the frequency

Brighter light means more photons, so more electrons, but each photon still has E = hf. Only a higher frequency gives faster electrons.

Ordinary Level

Asked on 7 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q6(l)
2025Q6(l)
2024Not asked
2023Not asked
2022Q12
2021Q6(l)
2019Not asked
2018Q5(j)
2017Q5(i)
2016Q5(i)

Links open the State Examinations Commission’s paper for that year.

More The photoelectric effect questions

The photoelectric effect, 2 marks

What is a photon?

  1. A particle found in the nucleus
  2. A positively charged electron
  3. A packet of electromagnetic energy
Show the answer

A packet of electromagnetic energy

Light comes in small packets (quanta) called photons. Each has energy E = hf, so higher frequency means more energy.

The photoelectric effect, 2 marks

Give one application of the photoelectric effect.

  1. A transformer in a phone charger
  2. A photocell in an automatic door or burglar alarm
  3. An X-ray machine for finding broken bones
Show the answer

A photocell in an automatic door or burglar alarm

Light falling on a photocell releases electrons and a current flows. Breaking the light beam stops the current and triggers the door or alarm.

The photoelectric effect, 2 marks

Light shines on the cathode of a photocell. What happens?

  1. Electrons are released and a current flows
  2. The cathode heats up until it melts
  3. Protons are released and flow across the tube
Show the answer

Electrons are released and a current flows

This is the photoelectric effect. Photocells are used in automatic doors, burglar alarms and light meters.

Other Physics topics

All of Leaving Cert Physics