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 electromagnetic spectrum

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

HL Asked on 4 of the last 10 Higher Level papers, most recently in 2024.

OL Asked on 4 of the last 10 Ordinary Level papers, most recently in 2026.

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 electromagnetic spectrum, Higher Level(6 marks)

Quick ones on The electromagnetic spectrum.

(a)Speed of all electromagnetic waves in a vacuum?
  1. 3.0 × 10⁶ m s⁻¹
  2. 3.0 × 10⁸ m s⁻¹
  3. 340 m s⁻¹
(b)Which part of the electromagnetic spectrum has the longest wavelength?
  1. X-rays
  2. Gamma rays
  3. Radio waves
(c)Which radiation lies just beyond the red end of the visible spectrum?
  1. Infrared
  2. X-rays
  3. Ultraviolet
Show the answers

(a) 3.0 × 10⁸ m s⁻¹

(b) Radio waves

(c) Infrared

Your turn: Higher Level questions on The electromagnetic spectrum.

Higher Level

Asked on 4 of the last 10 Higher Level papers, most recently in 2024.

Every paper, year by year

YearWhere it came up
2026Not asked
2025Not asked
2024Q13
2023Not asked
2022Not asked
2021Q8
2019Q5(a), Q6
2018Q9
2017Not asked
2016Not asked

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

More The electromagnetic spectrum questions

The electromagnetic spectrum, 2 marks

Which electromagnetic radiations are ionising?

  1. Radio waves, microwaves and low-frequency infrared
  2. Infrared, visible light and low-frequency ultraviolet
  3. High-frequency ultraviolet, X-rays and gamma rays
Show the answer

High-frequency ultraviolet, X-rays and gamma rays

Ionising photons carry enough energy (E = hf) to knock electrons out of atoms, damaging cells. Only the high-frequency end of the spectrum can do this.

The electromagnetic spectrum, 2 marks

Why does white light split into colours in a glass prism?

  1. The prism adds colours to the light
  2. Glass has a slightly different refractive index for each colour
  3. Each colour travels at a different speed in a vacuum
Show the answer

Glass has a slightly different refractive index for each colour

Violet slows most in glass, so it has the largest refractive index and bends most; red bends least. This is dispersion.

Ordinary Level

Asked on 4 of the last 10 Ordinary Level papers, most recently in 2026.

Every paper, year by year

YearWhere it came up
2026Q6(i)
2025Not asked
2024Not asked
2023Q6(i)
2022Q13
2021Not asked
2019Not asked
2018Q12(b)
2017Not asked
2016Not asked

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

More The electromagnetic spectrum questions

The electromagnetic spectrum, 2 marks

Which electromagnetic radiation has the highest frequency?

  1. Radio waves
  2. Visible light
  3. Gamma rays
Show the answer

Gamma rays

Order from highest frequency: gamma, X-rays, UV, visible, infrared, microwaves, radio. Radio waves have the lowest frequency.

The electromagnetic spectrum, 2 marks

How can ultraviolet radiation be detected?

  1. With a microphone
  2. It makes certain substances glow (fluoresce)
  3. With a thermometer that has a blackened bulb
Show the answer

It makes certain substances glow (fluoresce)

Washing powders and banknote inks glow under UV light. A blackened thermometer detects infrared, not UV.

The electromagnetic spectrum, 2 marks

What is solar irradiance?

  1. The power from the Sun falling on each square metre
  2. The temperature of the surface of the Sun
  3. The total energy the Sun gives out in one year
Show the answer

The power from the Sun falling on each square metre

Irradiance = power ÷ area, in W m⁻². It is higher in summer and at midday, when the Sun is high in the sky.

Other Physics topics

All of Leaving Cert Physics