NDA Physics · Modern Physics

Scientists and Discoveries: Match the Pair

A pure-recall table of who discovered or explained what in modern physics — Chadwick (neutron), Einstein (photoelectric effect, relativity), Marie Curie (radium), and the LIGO confirmation of gravitational waves.

All Modern Physics notes NDA Physics strategy

Why this matters

Three PYQs, all match-the-pair recall. The NDA presents a list of scientist-discovery pairs and asks which are correctly matched, so the only preparation is memorising the table cold. Get the famous swaps right (Chadwick = neutron, not photoelectric effect) and these are free marks.

Concept 1 of 2

Key modern-physics discoveries and their scientists

Intuition

Almost every modern-physics recall question reduces to matching a person to their landmark result. Build the table once, in order, and the match-the-pair questions become a lookup. Pay special attention to the famous swaps the exam plants — Chadwick discovered the neutron, Einstein explained the photoelectric effect, Marie Curie discovered radium.

Definition

Landmark discoveries and their scientists:

James Chadwick — discovered the neutron.
Albert Einstein — explained the photoelectric effect; gave relativity and $E = mc^2$ .
Marie Curie — discovered radium (and polonium); pioneered radioactivity research.
Rutherford — discovered the nucleus (alpha scattering).
J. J. Thomson — discovered the electron.
Niels Bohr — model of stable electron orbits.

Scientist	Discovery / contribution
James Chadwick	Neutron
Albert Einstein	Photoelectric effect explanation; relativity (E = mc²)
Marie Curie	Radium (and polonium); radioactivity NDA 2021 — in the match list, only "Marie Curie : Radium" was correctly matched (Chadwick was wrongly paired with photoelectric effect, Einstein with neutron).
Ernest Rutherford	Atomic nucleus (alpha scattering)
J. J. Thomson	Electron (cathode rays)
Niels Bohr	Stable electron orbits (Bohr model)

The exam plants swaps: Chadwick is the NEUTRON (not photoelectric), Einstein is the PHOTOELECTRIC EFFECT (not the neutron), Curie is RADIUM.

Practice this conceptself-check · 4 quick reps

Try it yourself

In the list — 1. Chadwick : Photoelectric effect, 2. Einstein : Neutron, 3. Marie Curie : Radium — which pairs are correctly matched?

Practice — Level 1 (4 reps)

Quick reps to lock in the method. Try each, then check.

1.
Who discovered the neutron?
2.
Who discovered radium?
3.
Who explained the photoelectric effect?
4.
Who discovered the electron?

From the bank · past-year question

Example 1Modern PhysicsMODERATE

Which of the following pairs of physical phenomenon and the discoverer is/are correctly matched ? 1. James Chadwick : Photoelectric effect 2. Albert Einstein : Neutron 3. Marie Curie : Radium Select the correct answer using the code given below :

[Q53 · Apr · 2021]

Chadwick = neutron, Einstein = photoelectric effect

The favourite swap pairs Chadwick with the photoelectric effect and Einstein with the neutron — both wrong. Chadwick discovered the neutron; Einstein explained the photoelectric effect.

Concept 2 of 2

LIGO — confirming gravitational waves and general relativity

Intuition

Einstein's general theory of relativity (1915) predicted that violent cosmic events should ripple spacetime, producing gravitational waves. A century later, the LIGO detectors directly measured such a ripple from two merging black holes, confirming the prediction. The exam tests what LIGO confirmed (general relativity) and, alongside, its full form as an acronym.

Definition

LIGO = Laser Interferometer Gravitational-wave Observatory.

LIGO made the first direct detection of gravitational waves (2015).
This confirmed a key prediction of Einstein's General Theory of Relativity.
A separate but related recall fact: LED = Light Emitting Diode (a semiconductor device that emits light when current flows).

Item	Fact
LIGO full form	Laser Interferometer Gravitational-wave Observatory
LIGO confirmed	Gravitational waves predicted by Einstein's General Theory of Relativity NDA 2024 — the LIGO experiment confirmed a prediction of the General Theory of Relativity.
LED full form	Light Emitting Diode (a semiconductor device)Q

LIGO detected gravitational waves and so confirmed General Relativity. LED is a Light Emitting Diode.

Practice this conceptself-check · 4 quick reps

Try it yourself

The LIGO experiment confirmed a prediction of which theory?

Practice — Level 1 (4 reps)

Quick reps to lock in the method. Try each, then check.

1.
LIGO confirmed a prediction of which theory?
2.
What does LIGO stand for?
3.
What did LIGO directly detect?
4.
What does LED stand for?

From the bank · past-year question

Example 2Modern PhysicsEASY

LIGO experiment confirmed one of the predictions of :

[Q131 · Apr · 2024]

LIGO confirmed GENERAL relativity (via gravitational waves)

Gravitational waves are a prediction of the GENERAL theory of relativity (the one about gravity and spacetime), not the special theory. LIGO's detection confirmed general relativity.

Drill 1 more on ligo — confirming gravitational waves and general relativity

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Reference tables (2)

Key modern-physics discoveries and their scientists6 rows

Scientist	Discovery / contribution
James Chadwick	Neutron
Albert Einstein	Photoelectric effect explanation; relativity (E = mc²)
Marie Curie	Radium (and polonium); radioactivity NDA 2021 — in the match list, only "Marie Curie : Radium" was correctly matched (Chadwick was wrongly paired with photoelectric effect, Einstein with neutron).
Ernest Rutherford	Atomic nucleus (alpha scattering)
J. J. Thomson	Electron (cathode rays)
Niels Bohr	Stable electron orbits (Bohr model)

The exam plants swaps: Chadwick is the NEUTRON (not photoelectric), Einstein is the PHOTOELECTRIC EFFECT (not the neutron), Curie is RADIUM.

LIGO — confirming gravitational waves and general relativity3 rows

Item	Fact
LIGO full form	Laser Interferometer Gravitational-wave Observatory
LIGO confirmed	Gravitational waves predicted by Einstein's General Theory of Relativity NDA 2024 — the LIGO experiment confirmed a prediction of the General Theory of Relativity.
LED full form	Light Emitting Diode (a semiconductor device)Q

LIGO detected gravitational waves and so confirmed General Relativity. LED is a Light Emitting Diode.

Watch out for (2)

Chadwick = neutron, Einstein = photoelectric effect
→ Key modern-physics discoveries and their scientists
LIGO confirmed GENERAL relativity (via gravitational waves)
→ LIGO — confirming gravitational waves and general relativity

Mastery check — 1 interleaved questions

Try each one before clicking. Questions are interleaved across the concepts above, not grouped — interleaving sharpens transfer.

Example 1Modern PhysicsEASY

LED (a semi-conductor device) is an abbreviation that stands for

[Q54 · Apr · 2021]

Drill every past-year question on this subtopic

3 questions from the bank — paginated, with cart and Word-export support.

Drill the 3 questions