NEET UG · Physics · Wave Optics

Single Slit Diffraction: NEET previous year questions

8 questions in ten years of NEET, in 5 of 10 papers. Pattern: Every year. Here is how it is asked and which ideas come back.

Asked in 10 years: 8; about 0.8 per paper
Years asked: 5/10; last asked 2025
Chance of a question next paper: 64%; historical rate, how we compute it
Weighted estimate: 0.7; model; history: 0.8 a paper on average, typically 0–2

Key findings

01
Asked in 5 of 10 papers, 8 questions in all: #104 of 204 topics by ten-year total. It comes back every 2.0 years on average. Last asked in 2025.
02
17% of its questions since 2018 tested an idea never asked before; 3 repeated an idea from the year before.
03
The most repeated idea is Polarisation and Malus's Law, asked 6 times (2017, 2018, 2020, 2024, 2025), usually as “true statement selection on brewster's angle”.
04
NEET has asked 1 of the 75 ideas in this topic; 74 have never been asked, directly or indirectly.
05
Mostly asked as one-line MCQ (50%); 50% easy, 0% hard.

Questions per year

Up to 2023: 0.7; per paper
Since 2024: 1.0; 0.3
Usual gap: 2.0 yrs; between papers asking it
Swing: ±0.9; questions, year to year

How it is asked

Difficulty, format and skill

Across all 8 questions on Single Slit Diffraction since 2017.

Difficulty

QUESTIONS

Easy4 · 50%
Medium4 · 50%
Hard0 · 0%

Format

One-line MCQ · 4 Q50%
Numerical · 4 Q50%

Skill tested

Calculation · 4 Q50%
Concept · 3 Q38%
Application · 1 Q13%

Repeats

New idea, or one asked before?

Each column is a paper. Blue questions tested an idea NEET had not asked before; navy ones went back to an idea from an earlier paper. 2017 is the first paper, so everything in it counts as new.

’17’18’19’20’21’22’23’24’25’26

Idea asked for the first time
Idea asked in an earlier paper

Coverage of the topic

NEET has asked 1 of the 75 ideas in this topic. 74 have never been asked yet.

Asked directly1 · 1%
Touched inside another question0 · 0%
Never asked74 · 99%

Ideas come from Lumi’s syllabus map of NCERT. A never-asked idea is not a safe skip: most new questions come from exactly these.

Drill down

Idea, year, question

Every idea NEET tested in this topic, with its ten papers. Open one to read the questions.

ideaAskedShareYears’17’18’19’20’21’22’23’24’25’26

Repeated6 · 75%75%5/102
- 2025 · Q27
  An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then-
  easyOne-line MCQAsked the year before
- 2025 · Q43
  The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5° from the polarization axis of one…
  mediumNumericalAsked the year before
- 2024 · Q2
  An unpolarised light beam strikes a glass surface at Brewster's angle. Then
  easyOne-line MCQ
- 2020 · Q138
  The Brewsters angle $i_b$ for an interface should be :
  mediumOne-line MCQ
- 2018 · Q8
  Unpolarised light is incident from air on a plane surface of a material of refractive index ' $\mu$ '. At a particular angle of incidence…
  mediumOne-line MCQAsked the year before
- 2017 · Q37
  Two Polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_0$ is incident on $P_1$ . A…
  easyNumericalNew idea
1 · 13%13%1/10
1 · 13%13%1/10

Squares are the ten papers, 2017 to 2026; darker means more questions. Share is of the level above.

Ideas

Every idea inside this topic

3 different ideas were tested; 1 came more than once. Angular Radius of Airy Disk is the foundation for 1 other ideas in the syllabus.

Polarisation and Malus's Law6×
true statement selection on brewster's angle
One-line MCQ · 11% next
Angular Radius of Airy Disk1×
numerical
Numerical · 4% next · foundation for 1
Resolving Power of Instruments1×
ratio of resolving powers for two wavelengths
Numerical · 4% next

Idea	Times	Format	Chance next	Foundation for
Polarisation and Malus's Lawtrue statement selection on brewster's angle	6	One-line MCQConcept	11%	–
Angular Radius of Airy Disknumerical	1	NumericalCalculation	4%	1 ideas
Resolving Power of Instrumentsratio of resolving powers for two wavelengths	1	NumericalCalculation	4%	–

Chance next is the historical rate at which an idea with this record came back in the following paper. It is low for every idea, which is why learning the topic beats memorising past questions. All repeated ideas

Every question

Single Slit Diffraction questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it tested.

NEET 20252 questions

Q27
An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then-
Idea: Polarisation and Malus's Law
Asked last yearEasyOne-line MCQ
Q43
The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5° from the polarization axis of one…
Idea: Polarisation and Malus's Law
Asked last yearMediumNumerical

NEET 20241 question

Q2
An unpolarised light beam strikes a glass surface at Brewster's angle. Then
Idea: Polarisation and Malus's Law
EasyOne-line MCQ

NEET 20202 questions

Q138
The Brewsters angle $i_b$ for an interface should be :
Idea: Polarisation and Malus's Law
MediumOne-line MCQ
Q168
Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m…
Idea: Angular Radius of Airy Disk
New ideaMediumNumerical

NEET 20181 question

Q8
Unpolarised light is incident from air on a plane surface of a material of refractive index ' $\mu$ '. At a particular angle of incidence…
Idea: Polarisation and Malus's Law
Asked last yearMediumOne-line MCQ

NEET 20172 questions

Q33
The ratio of resolving powers of an optical microscope for two wavelengths $\lambda_1$ = 4000 Å and $\lambda_2$ = 6000 Å is :
Idea: Resolving Power of Instruments
EasyNumerical
Q37
Two Polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_0$ is incident on $P_1$ . A…
Idea: Polarisation and Malus's Law
EasyNumerical

Questions from the official NEET UG papers published by NTA (CBSE before 2019). Topic and idea tags, counts and notes are Lumi’s.