JEE Mains Previous Years Questions with Solutions Android App

Download our App

JEE Mains Previous Years Questions with Solutions

4.5 
Star 1 Star 2 Star 3 Star 4
Star 5
  (100k+ )
1

JEE Main 2021 (Online) 31st August Morning Shift

MCQ (Single Correct Answer)
A moving proton and electron have the same de-Broglie wavelength. If K and P denote the K.E. and momentum respectively. Then choose the correct option :
A
Kp < Ke and Pp = Pe
B
Kp = Ke and Pp = Pe
C
Kp < Ke an Pp < Pe
D
Kp > Ke and Pp = Pe

Explanation

$${\lambda _p} = {h \over {{P_p}}}$$

$${\lambda _e} = {h \over {{P_e}}}$$

$$\because$$ $${\lambda _p} = {\lambda _e}$$

$$ \Rightarrow {P_p} = {P_e}$$

$${(K)_p} = {{P_p^2} \over {2{m_p}}}$$

$${(K)_e} = {{P_e^2} \over {2{m_e}}}$$

Kp < Ke as mp > me

Option (a)
2

JEE Main 2021 (Online) 31st August Morning Shift

MCQ (Single Correct Answer)
A sample of a radioactive nucleus A disintegrates to another radioactive nucleus B, which in turn disintegrates to some other stable nucleus C. Plot of a graph showing the variation of number of atoms of nucleus B versus time is :

(Assume that at t = 0, there are no B atoms in the sample)
A
B
C
D

Explanation

A $$\to$$ B $$\to$$ C (stable)

Initially no. of atoms of B = 0 at t = 0, no. of atoms of B will starts increasing & reaches maximum value when rate of decay of B = rate of formation of B.

After that maximum value, no. of atoms will starts decreasing as growth & decay both are exponential functions, so best possible graph is (d).
3

JEE Main 2021 (Online) 27th August Morning Shift

MCQ (Single Correct Answer)
There are 1010 radioactive nuclei in a given radioactive element, its half-life time is 1 minute. How many nuclei will remain after 30 seconds? $$\left( {\sqrt 2 = 1.414} \right)$$
A
2 $$\times$$ 1010
B
7 $$\times$$ 109
C
105
D
4 $$\times$$ 1010

Explanation

$${N \over {{N_0}}} = {\left( {{1 \over 2}} \right)^{{t \over {{t^{1/2}}}}}}$$

$${N \over {{{10}^{10}}}} = {\left( {{1 \over 2}} \right)^{{{30} \over {60}}}}$$

$$ \Rightarrow N = {10^{10}} \times {\left( {{1 \over 2}} \right)^{{1 \over 2}}} = {{{{10}^{10}}} \over {\sqrt 2 }} \approx 7 \times {10^9}$$
4

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)
At time t = 0, a material is composed of two radioactive atoms A and B, where NA(0) = 2NB(0). The decay constant of both kind of radioactive atoms is $$\lambda$$. However, A disintegrates to B and B disintegrates to C. Which of the following figures represents the evolution of NB(t) / NB(0) with respect to time t?

[NA (0) = No. of A atoms at t = 0

NB (0) = No. of B atoms at t = 0]
A
B
C
D

Explanation

A $$\to$$ B, B $$\to$$ C

$${{d{N_B}} \over {dt}} = \lambda {N_A} - \lambda {N_B}$$

$${{d{N_B}} \over {dt}} = 2\lambda {N_{{B_0}}}{e^{ - \lambda t}} - \lambda {N_B}$$

$${e^{ - \lambda t}}\left( {{{d{N_B}} \over {dt}} + \lambda {N_B}} \right) = 2\lambda {N_{{B_0}}}{e^{ - \lambda t}} \times {e^{\lambda t}}$$

$${d \over {dt}}({N_B}{e^{\lambda t}}) = 2\lambda {N_{{B_0}}}$$, on integrating

$${N_B}{e^{\lambda t}} = 2\lambda t{N_{{B_0}}} + {N_{{B_0}}}$$

$${N_B} = {N_{{B_0}}}[1 + 2\lambda t]{e^{ - \lambda t}}$$

$${{d{N_B}} \over {dt}} = 0$$ at $$ - \lambda [1 + 2\lambda t){e^{ - \lambda t}} + 2\lambda {e^{ - \lambda t}} = 0$$

$${N_{{B_{\max }}}}$$ at $$t = {1 \over {2\lambda }}$$

Questions Asked from Atoms and Nuclei

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2021 (Online) 31st August Morning Shift (2)
JEE Main 2021 (Online) 27th August Morning Shift (1)
JEE Main 2021 (Online) 26th August Evening Shift (1)
JEE Main 2021 (Online) 26th August Morning Shift (1)
JEE Main 2021 (Online) 27th July Evening Shift (2)
JEE Main 2021 (Online) 25th July Evening Shift (1)
JEE Main 2021 (Online) 25th July Morning Shift (2)
JEE Main 2021 (Online) 22th July Evening Shift (2)
JEE Main 2021 (Online) 20th July Evening Shift (1)
JEE Main 2021 (Online) 20th July Morning Shift (2)
JEE Main 2021 (Online) 18th March Evening Shift (3)
JEE Main 2021 (Online) 18th March Morning Shift (3)
JEE Main 2021 (Online) 17th March Evening Shift (1)
JEE Main 2021 (Online) 17th March Morning Shift (3)
JEE Main 2021 (Online) 16th March Evening Shift (3)
JEE Main 2021 (Online) 26th February Evening Shift (1)
JEE Main 2021 (Online) 26th February Morning Shift (1)
JEE Main 2021 (Online) 25th February Evening Shift (1)
JEE Main 2021 (Online) 25th February Morning Shift (1)
JEE Main 2021 (Online) 24th February Evening Shift (1)
JEE Main 2021 (Online) 24th February Morning Shift (1)
JEE Main 2020 (Online) 6th September Evening Slot (1)
JEE Main 2020 (Online) 5th September Evening Slot (1)
JEE Main 2020 (Online) 5th September Morning Slot (1)
JEE Main 2020 (Online) 3rd September Evening Slot (2)
JEE Main 2020 (Online) 3rd September Morning Slot (1)
JEE Main 2020 (Online) 2nd September Evening Slot (1)
JEE Main 2020 (Online) 2nd September Morning Slot (1)
JEE Main 2020 (Online) 8th January Evening Slot (1)
JEE Main 2020 (Online) 8th January Morning Slot (2)
JEE Main 2020 (Online) 7th January Morning Slot (1)
JEE Main 2019 (Online) 12th April Evening Slot (2)
JEE Main 2019 (Online) 12th April Morning Slot (1)
JEE Main 2019 (Online) 10th April Evening Slot (2)
JEE Main 2019 (Online) 10th April Morning Slot (1)
JEE Main 2019 (Online) 9th April Evening Slot (1)
JEE Main 2019 (Online) 9th April Morning Slot (1)
JEE Main 2019 (Online) 8th April Evening Slot (1)
JEE Main 2019 (Online) 8th April Morning Slot (1)
JEE Main 2019 (Online) 12th January Evening Slot (1)
JEE Main 2019 (Online) 12th January Morning Slot (1)
JEE Main 2019 (Online) 11th January Evening Slot (1)
JEE Main 2019 (Online) 11th January Morning Slot (1)
JEE Main 2019 (Online) 10th January Evening Slot (1)
JEE Main 2019 (Online) 10th January Morning Slot (1)
JEE Main 2019 (Online) 9th January Evening Slot (1)
JEE Main 2019 (Online) 9th January Morning Slot (1)
JEE Main 2018 (Online) 16th April Morning Slot (2)
JEE Main 2018 (Offline) (3)
JEE Main 2018 (Online) 15th April Evening Slot (2)
JEE Main 2018 (Online) 15th April Morning Slot (2)
JEE Main 2017 (Online) 9th April Morning Slot (2)
JEE Main 2017 (Online) 8th April Morning Slot (2)
JEE Main 2017 (Offline) (2)
JEE Main 2016 (Online) 9th April Morning Slot (1)
JEE Main 2016 (Offline) (1)
JEE Main 2015 (Offline) (1)
JEE Main 2014 (Offline) (2)
JEE Main 2013 (Offline) (1)
AIEEE 2012 (3)
AIEEE 2011 (2)
AIEEE 2010 (3)
AIEEE 2009 (2)
AIEEE 2008 (2)
AIEEE 2007 (4)
AIEEE 2006 (5)
AIEEE 2005 (5)
AIEEE 2004 (3)
AIEEE 2003 (9)
AIEEE 2002 (3)

Joint Entrance Examination

JEE Main JEE Advanced WB JEE

Graduate Aptitude Test in Engineering

GATE CSE GATE ECE GATE EE GATE ME GATE CE GATE PI GATE IN

Medical

NEET

CBSE

Class 12