JEE Main · Physics · Thermal Properties of Matter
Thermal Radiation: JEE Main previous year questions
11 questions in the 108 JEE Main shifts Lumi analysed, in 6 of 8 years. Pattern: Asked most years. 3 came in 2024–26. Here is how it is asked and which ideas come back.
- Questions
- 11
- in 11 of 108 shifts
- Years asked
- 6/8
- last asked 2025
- Weighted estimate
- 0.1
- model; history: 0.1 a shift on average, typically 0.0–0.1
Key findings
- 01
Asked in 6 of 8 years with analysed shifts and in 11 of 108 shifts: 11 questions, #176 of 196 topics. Last asked in 2025.
- 02
45% of its questions since 2020 tested an idea no earlier year had asked; 4 repeated an idea from the year before.
- 03
The most repeated idea is Thermal Radiation Pressure, asked 3 times in 3 shifts (2022, 2024, 2025), most often as “radiation pressure from source power”.
- 04
JEE Main has asked 5 of the 57 ideas in this topic; 50 have never been asked, directly or inside another question.
- 05
Mostly asked as single correct (55%); 27% need a numerical answer, 9% are easy and 0% hard.
- 06
The skill tested most is calculation (64%), then data or graph (18%).
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: 1 in 12 shifts · 2021: 2 in 24 shifts · 2022: 3 in 24 shifts · 2023: 2 in 12 shifts · 2024: 1 in 18 shifts · 2025: 2 in 8 shifts · 2026: 0 in 9 shifts.
- Up to 2023
- 0.1
- a shift, of 25
- Since 2024
- 0.1
- 0.0
- Usual gap
- 1.0 yrs
- between years asking it
- Shifts with it
- 11/108
- 10% of analysed shifts
How it is asked
Difficulty, format and skill
Across all 11 questions on Thermal Radiation since 2017.
Difficulty
QUESTIONS- Easy1 · 9%
- Medium10 · 91%
- Hard0 · 0%
Format
SHARE- Single correct · 6 Q55%
- Numerical value · 3 Q27%
- Other · 1 Q9%
- Diagram based · 1 Q9%
Skill tested
SHARE- Calculation · 7 Q64%
- Data or graph · 2 Q18%
- Multi-step · 1 Q9%
- Application · 1 Q9%
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.
- Idea asked for the first time
- Idea asked in an earlier year
Coverage of the topic
JEE Main has asked 5 of the 57 ideas in this topic. 50 have never been asked yet.
- Asked directly5 · 9%
- Touched inside another question2 · 4%
- Never asked50 · 88%
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
Chapter, idea, question
Every idea JEE Main tested in this topic, with its eight years. Open one to read the questions.
4 ideas inside
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
5 different ideas were tested; 4 came more than once.
radiation pressure from source power
Single correct · 3 shiftstemperature after successive cooling intervals
Numerical value · 3 shifts · 1 numericalcooling time by average temperature method
Single correct · 2 shiftsgraph interpretation of newton's law of cooling
Diagram based · 2 shifts · 1 numericalemissivity from radiated power
Numerical value · 1 shift · 1 numerical
| Idea | Years asked | Times | Shifts | Format | Numerical |
|---|---|---|---|---|---|
| Thermal Radiation Pressureradiation pressure from source power | 3 | 3 | Single correctCalculation | – | |
| Newton's Law of Coolingtemperature after successive cooling intervals | 3 | 3 | Numerical valueCalculation | 1 | |
| Average Temperature Method for Newton's Law of Coolingcooling time by average temperature method | 2 | 2 | Single correctCalculation | – | |
| Logarithmic Graph of Newton's Law of Coolinggraph interpretation of newton's law of cooling | 2 | 2 | Diagram basedData or graph | 1 | |
| Stefan-Boltzmann Lawemissivity from radiated power | 1 | 1 | Numerical valueCalculation | 1 |
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
Thermal Radiation 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.
JEE Main 20252 questions in 2 shifts
- 3 Apr, Shift 1Q40The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2m away from it, is
Idea: Thermal Radiation Pressure
Asked the year beforeMediumSingle correct - 7 Apr, Shift 1Q47A wire of length 10 cm and diameter 0.5 mm is used in a bulb. The temperature of the wire is C and power radiated by the wire…
Idea: Stefan-Boltzmann Law
New ideaMediumNumerical value
JEE Main 20241 question in 1 shift
- 8 Apr, Shift 1Q42Average force exerted on a non-reflecting surface at normal incidence is N. If 360 W/cm is the light energy flux…
Idea: Thermal Radiation Pressure
MediumSingle correct
JEE Main 20232 questions in 2 shifts
- 6 Apr, Shift 2Q38A body cools in 7 minutes from C to C. The temperature of the surrounding is C. The temperature of the body…
Idea: Newton's Law of Cooling
Asked the year beforeMediumSingle correct - 12 Apr, Shift 1Q37A body cools from C to C in 5 minutes. The temperature of the surrounding is C. The time it takes to cool…
Idea: Average Temperature Method for Newton's Law of Cooling
MediumSingle correct
JEE Main 20223 questions in 3 shifts
- 27 Jul, Shift 1Q38Read the following statements : A. When small temperature difference between a liquid and its surrounding is doubled, the rate of loss of…
Idea: Newton's Law of Cooling
Asked the year beforeMediumOther - 28 Jul, Shift 2Q15Sun light falls normally on a surface of area and exerts an average force of N within a time period…
Idea: Thermal Radiation Pressure
New ideaMediumSingle correct - 24 Jun, Shift 2Q60In an experiment to verify Newton’s law of cooling, a graph is plotted between, the temperature difference (T) of the water and…
Idea: Logarithmic Graph of Newton's Law of Cooling
Asked the year beforeMediumNumerical value · figure
JEE Main 20212 questions in 2 shifts
- 4 Aug, Shift 2Q15Which is the correct graph to explain the Newton’s law of cooling. T and are the temperatures of hot body and surrounding…
Idea: Logarithmic Graph of Newton's Law of Cooling
New ideaEasyDiagram based · figure - 22 Jul, Shift 2Q23In 5 minutes, a body cools from 75°C to 65°C at room temperature of 25°C. The temperature of body at the end of next 5 minutes is ________…
Idea: Newton's Law of Cooling
New ideaMediumNumerical value
JEE Main 20201 question in 1 shift
- 3 Sep, Shift 2Q6A metallic sphere cools from C to C in 300 s. If atmospheric temperature around is C, then the sphere's…
Idea: Average Temperature Method for Newton's Law of Cooling
New ideaMediumSingle correct
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.