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Leaving Cert Physics: Doppler effect

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

HL Asked on 8 of the last 10 Higher Level papers, most recently in 2026. most years

OL Asked on 6 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.

Doppler effect, Higher Level(8 marks)

Quick ones on Doppler effect.

(a)A siren is moving towards you. The frequency you hear is?
  1. Lower than the frequency emitted
  2. Higher than the frequency emitted
  3. Exactly the frequency emitted
(b)What does the red shift in the light from distant galaxies show?
  1. They are very close to us
  2. They are made of hot hydrogen
  3. They are moving away from us
(c)Give one medical use of the Doppler effect.
  1. Measuring the speed of blood flow using ultrasound
  2. Measuring body temperature from infrared radiation
  3. Imaging a broken bone by passing waves through it
Show the answers

(a) Higher than the frequency emitted

(b) They are moving away from us

(c) Measuring the speed of blood flow using ultrasound

Your turn: Higher Level questions on Doppler effect.

Higher Level

Asked on 8 of the last 10 Higher Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q14(b)
2025Q6(i)
2024Not asked
2023Q14(b)
2022Q14(b)
2021Q14(b)
2019Not asked
2018Q5(d)
2017Q7
2016Q12(c)

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

More Doppler effect questions

Doppler effect, 3 marks

Define the Doppler effect.

  1. The spreading of a wave as it passes through a gap about the same size as its wavelength
  2. The apparent change in the speed of a wave due to a change in the medium it travels through
  3. The apparent change in the frequency of a wave due to relative motion between the source and the observer
Show the answer

The apparent change in the frequency of a wave due to relative motion between the source and the observer

The source catches up on its own waves, shortening the wavelength ahead and stretching it behind, so pitch rises on approach and falls once it passes.

Ordinary Level

Asked on 6 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q11
2025Q14(b)
2024Q6(f)
2023Not asked
2022Not asked
2021Q6(e)
2019Q7
2018Not asked
2017Q8
2016Not asked

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

More Doppler effect questions

Doppler effect, 2 marks

A car sounds its horn as it moves away from you. The pitch you hear is?

  1. Higher than the note the horn gives out
  2. The same as the note the horn gives out
  3. Lower than the note the horn gives out
Show the answer

Lower than the note the horn gives out

As the source moves away the waves are stretched out, so fewer reach you each second. A lower frequency means a lower pitch.

Doppler effect, 2 marks

Give one use of the Doppler effect.

  1. Seeing broken bones
  2. Police radar speed checks
  3. Measuring the depth of the sea by echo
Show the answer

Police radar speed checks

Radar guns measure the change in frequency of waves reflected off a moving car. Echo sounding uses reflection; broken bones need X-rays.

Doppler effect, 2 marks

In the Doppler effect, does the source itself give out a different frequency?

  1. No, only the frequency received by the observer changes
  2. Yes, it gives out a higher frequency as it moves
  3. Yes, it gives out a lower frequency as it moves away from you
Show the answer

No, only the frequency received by the observer changes

The source's frequency does not change. Relative motion changes how many waves reach the observer each second.

Other Physics topics

All of Leaving Cert Physics