JEE Main · Physics · Ray Optics and Optical Instruments

Prism Deviation: JEE Main previous year questions

Name: Prism Deviation: JEE Main previous year questions
Creator: Lumi

21 questions in the 108 JEE Main shifts Lumi analysed, in 6 of 8 years. Pattern: Asked most years. 10 came in 2024–26. Here is how it is asked and which ideas come back.

Questions: 21; in 21 of 108 shifts
Years asked: 6/8; last asked 2026
Chance in a shift: 30%; calibrated model, how we compute it
Weighted estimate: 0.2; model; history: 0.2 a shift on average, typically 0.0–0.3

Key findings

01
Asked in 6 of 8 years with analysed shifts and in 21 of 108 shifts: 21 questions, #141 of 196 topics.
02
48% of its questions since 2020 tested an idea no earlier year had asked; 6 repeated an idea from the year before.
03
The most repeated idea is Minimum Deviation Condition, asked 9 times in 9 shifts (2021, 2022, 2024, 2025, 2026), most often as “ratio of angles for thin prism at minimum deviation”.
04
JEE Main has asked 9 of the 59 ideas in this topic; 46 have never been asked, directly or inside another question.
05
Mostly asked as numerical value (48%); 48% need a numerical answer, 24% are easy and 5% hard. It went up from 0.1 to 0.3 questions a shift since 2024.
06
The skill tested most is calculation (43%), then multi-step (33%).

Questions a shift, year by year

Out of the 25 Physics questions in a shift. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift.

Raw count: 2017: 0 in 1 shift · 2020: 0 in 12 shifts · 2021: 6 in 24 shifts · 2022: 4 in 24 shifts · 2023: 1 in 12 shifts · 2024: 4 in 18 shifts · 2025: 2 in 8 shifts · 2026: 4 in 9 shifts.

Up to 2023: 0.1; a shift, of 25
Since 2024: 0.3; 0.2
Usual gap: 1.0 yrs; between years asking it
Shifts with it: 21/108; 19% of analysed shifts

How it is asked

Difficulty, format and skill

Across all 21 questions on Prism Deviation since 2017.

Difficulty

QUESTIONS

515

Easy5 · 24%
Medium15 · 71%
Hard1 · 5%

Format

Numerical value · 10 Q48%
Single correct · 9 Q43%
Other · 1 Q5%
Two statements · 1 Q5%

Skill tested

Calculation · 9 Q43%
Multi-step · 7 Q33%
Application · 3 Q14%
Conceptual · 2 Q10%

Repeats

New idea, or one asked before?

Each column is a year. Blue questions tested an idea no earlier year had asked; navy ones went back to an idea from an earlier year. 2017 is the first year, so everything in it counts as new. Heights are question counts, and Lumi analysed 1 to 24 shifts a year, so compare the split inside a column rather than heights across years.

’17’20’21’22’23’24’25’26

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

Coverage of the topic

JEE Main has asked 9 of the 59 ideas in this topic. 46 have never been asked yet.

946

Asked directly9 · 15%
Touched inside another question4 · 7%
Never asked46 · 78%

Ideas come from Lumi’s JEE syllabus map. A never-asked idea is not a safe skip: across all of JEE Main, 22% of questions since 2024 tested an idea no earlier year had asked.

Drill down

Idea, year, question

Every idea JEE Main tested in this topic, with its eight years. Open one to read the questions.

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

OpenRepeated9 · 43%43%5/8232
- 2 Apr ’26 S1 · Q40
  For a thin symmetric prism made of glass (refractive index $1.5$ ), the ratio of incident angle and minimum deviation will be _________.
  mediumSingle correctAsked the year before
- 5 Apr ’26 S1 · Q40
  A ray of light passing through an equilateral prism is having velocity $2.12 \times 10^8$ m/s in the prism material, then the minimum…
  mediumSingle correctAsked the year before
- 3 Apr ’25 S1 · Q41
  Consider following statements for refraction of light through prism, when angle of deviation is minimum. A. The refracted ray inside prism…
  mediumOtherAsked the year before
- 6 Apr ’24 S1 · Q51
  The refractive index of prism is $\mu = \sqrt{3}$ and the ratio of the angle of minimum deviation to the angle of prism is one. The value…
  mediumNumerical value
- 27 Jan ’24 S1 · Q45
  If the refractive index of the material of a prism is $\cot\left(\frac{A}{2}\right)$ , where A is the angle of prism then the angle of…
  mediumSingle correct
- 31 Jan ’24 S1 · Q45
  The refractive index of a prism with apex angle $A$ is $\cot A/2$ . The angle of minimum deviation is :
  mediumSingle correct
- 30 Jun ’22 S1 · Q58
  The refractive index of an equilateral prism is $\sqrt{2}$ . The angle of emergence under minimum deviation position of prism, in degree,…
  easyNumerical valueAsked the year before
- 22 Jul ’21 S2 · Q24
  A ray of light passing through a prism ( $\mu = \sqrt{3}$ ) suffers minimum deviation. It is found that the angle of incidence is double the…
  easyNumerical valueNew idea
- 25 Jul ’21 S2 · Q17
  A prism of refractive index $\mu$ and angle of prism A is placed in the position of minimum angle of deviation. If minimum angle of…
  mediumSingle correctNew idea
OpenRepeated3 · 14%14%3/8
OpenRepeated2 · 10%10%2/8
OpenRepeated2 · 10%10%2/8
Open1 · 5%5%1/8
Open1 · 5%5%1/8
Open1 · 5%5%1/8
Open1 · 5%5%1/8
Open1 · 5%5%1/8

Squares are the 8 years with analysed shifts, 2017 to 2026. A number is the questions that year when there is more than one; the shade is scaled to one shift, so a year with more analysed shifts (1 to 24 a year) does not look darker. Share is of the level above.

Ideas

Every idea inside this topic

9 different ideas were tested; 4 came more than once.

Minimum Deviation Condition9×
ratio of angles for thin prism at minimum deviation
Single correct · 9 shifts · 3 numerical
Prism Refractive Index3×
refractive index from minimum deviation
Single correct · 3 shifts · 1 numerical
TIR at Second Face Condition2×
condition for total internal reflection in prism
Numerical value · 2 shifts · 1 numerical
Achromatic Prism Combination2×
prism angle in achromatic combination
Numerical value · 2 shifts · 2 numerical
Angular Dispersion1×
statement i/ii on dispersion of white light
Two statements · 1 shift
Liquid-Filled Equilateral Prism1×
minimum deviation of liquid prism
Numerical value · 1 shift · 1 numerical
Grazing Emergence Condition1×
liquid index from grazing ray at prism face
Numerical value · 1 shift · 1 numerical
Base Parallel Property at Minimum Deviation1×
travel time of ray in prism at minimum deviation
Numerical value · 1 shift · 1 numerical
Prism in Surrounding Medium1×
change in minimum deviation on immersion
Single correct · 1 shift

Idea	Times	Shifts	Format	Numerical
Minimum Deviation Conditionratio of angles for thin prism at minimum deviation	9	9	Single correctCalculation	3
Prism Refractive Indexrefractive index from minimum deviation	3	3	Single correctCalculation	1
TIR at Second Face Conditioncondition for total internal reflection in prism	2	2	Numerical valueMulti-step	1
Achromatic Prism Combinationprism angle in achromatic combination	2	2	Numerical valueCalculation	2
Angular Dispersionstatement i/ii on dispersion of white light	1	1	Two statementsConceptual	–
Liquid-Filled Equilateral Prismminimum deviation of liquid prism	1	1	Numerical valueCalculation	1
Grazing Emergence Conditionliquid index from grazing ray at prism face	1	1	Numerical valueMulti-step	1
Base Parallel Property at Minimum Deviationtravel time of ray in prism at minimum deviation	1	1	Numerical valueMulti-step	1
Prism in Surrounding Mediumchange in minimum deviation on immersion	1	1	Single correctMulti-step	–

Times and shifts count every analysed shift. Across JEE Main, 78% of questions since 2024 went back to an idea an earlier year had asked; the rest were new. All repeated ideas

Every question

Prism Deviation questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it tested. Open one for its options and the official answer.

Questions from the official JEE Main Paper 1 shifts published by NTA (CBSE for 2017). Questions NTA dropped are left out. Topic and idea tags, counts and notes are Lumi’s.

Key findings

Questions a shift, year by year

Difficulty, format and skill

Difficulty

Format

Skill tested

New idea, or one asked before?

Coverage of the topic

Idea, year, question

Every idea inside this topic

Prism Deviation questions, year by year

JEE Main 20264 questions in 4 shifts

JEE Main 20252 questions in 2 shifts

JEE Main 20244 questions in 4 shifts

JEE Main 20231 question in 1 shift

JEE Main 20224 questions in 4 shifts

JEE Main 20216 questions in 6 shifts

More topics in Ray Optics and Optical Instruments