1
MCQ (Single Correct Answer)

JEE Main 2018 (Online) 16th April Morning Slot

Two sitar strings, A and B, playing the note 'Dha' are slightly out of tune and produce beats of frequency 5 Hz. The tension of the string B s slightly increased and the beat frequency is found to decrease by 3Hz. If the frequency of A is 425 Hz, the original frequency of B is :
A
430 Hz
B
420 Hz
C
428 Hz
D
422 Hz

Explanation

Frequency of B, fB = 425 $$ \pm $$ 5 = 420 or 430 Hz

As tension of string B is increased

So, frequency of B, fB should also increase [as f $$ \propto $$ $$\sqrt T $$]

If initially fB = 430 Hz then when fB increases by increasing the tension then fB $$-$$ fA increases that means beat frequency increase.

So, fB can't be 430 Hz

When fB = 420 then when fB increases fA $$-$$ fB decreases means beat frequency decreases. So, correct fB = 420 Hz.
2
MCQ (Single Correct Answer)

JEE Main 2018 (Online) 16th April Morning Slot

The end correction of a resonance column is 1 cm. If the shortest length resonating with the tunning fork is 10 cm, the next resonating length should be :
A
28 cm
B
32 cm
C
36 cm
D
40 c

Explanation

Given, End correction (e) = 1 cm

For first resonance,

$${\lambda \over 4} = {l_1} + e$$ = 10 + 1 = 11 cm

For second resonance,

$${3\lambda \over 4} = {l_2} + e$$

$$ \Rightarrow $$ $${l_2}$$ = 3 $$ \times $$ 11 - 1 = 32 cm
3
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 9th January Morning Slot

Two coherent sources produce waves of different intensities which interfere. After interference, the ratio of the maximum intensity to the minimum intensity is 16. The intensity of the waves are in the ratio :
A
16 : 9
B
25 : 9
C
4 : 1
D
5 : 3

Explanation

Given that,

$${{{{\rm I}_{\max }}} \over {{{\mathop{\rm I}\nolimits} _{min}}}} = {{16} \over 1}$$

We know,

Imax $$=$$ $${\left( {\sqrt {{{\rm I}_1}} + \sqrt {{{\rm I}_2}} } \right)^2}$$

and Imin $$ = {\left( {\sqrt {{{\rm I}_1}} - \sqrt {{{\rm I}_2}} } \right)^2}$$

$$ \therefore $$   $${{{{\left( {\sqrt {{{\rm I}_1}} + \sqrt {{{\rm I}_2}} } \right)}^2}} \over {{{\left( {\sqrt {{{\rm I}_1}} - \sqrt {{{\rm I}_2}} } \right)}^2}}} = {{16} \over 1}$$

$$ \Rightarrow $$   $${{\sqrt {{{\rm I}_1}} + \sqrt {{{\rm I}_2}} } \over {\sqrt {{{\rm I}_1}} - \sqrt {{{\rm I}_2}} }} = {4 \over 1}$$

$$ \Rightarrow $$   $$4\sqrt {{{\rm I}_1}} - 4\sqrt {{{\rm I}_2}} = \sqrt {{{\rm I}_1}} + \sqrt {{{\rm I}_2}} $$

$$ \Rightarrow $$   $$3\sqrt {{{\rm I}_1}} = 5\sqrt {{{\rm I}_2}} $$

$$ \Rightarrow $$   $${{\sqrt {{{\rm I}_1}} } \over {\sqrt {{{\rm I}_2}} }} = {5 \over 3}$$

$$ \Rightarrow $$   $${{{{\rm I}_1}} \over {{{\rm I}_2}}} = {{25} \over 9}$$
4
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 9th January Evening Slot

A rod of mass 'M' and length '2L' is suspended at its middle by a wire. It exhibits torsional oscillations; If two masses each of 'm' are attached at distance 'L/2' from its centre on both sides, it reduces the oscillation frequency by 20%. The value of radio m/M is close to :
A
0.77
B
0.57
C
0.37
D
0.17

Explanation

Initially :



After putting 2 masses of each 'm' at a distance $${L \over 2}$$ from center :



We know,

Time period (T) = 2$$\pi $$ $$\sqrt {{{\rm I} \over C}} $$

$$ \therefore $$  T $$ \propto $$ $$\sqrt {\rm I} $$

$$ \therefore $$   Frequency (f) $$ \propto $$ $$\sqrt {{1 \over {\rm I}}} $$

$$ \therefore $$   $${{{f_1}} \over {{f_2}}}$$ = $$\sqrt {{{{{\rm I}_2}} \over {{{\rm I}_1}}}} $$

Also given that,
After putting two masses 'm' at both end new frequency becomes 80% of initial frequency.

$$ \therefore $$   f2 = 0.8f1

$$ \therefore $$   $${{{f_1}} \over {0.8{f_1}}}$$ = $$\sqrt {{{{{\rm I}_2}} \over {{{\rm I}_1}}}} $$

$$ \therefore $$   $${{{{{\rm I}_1}} \over {{{\rm I}_2}}}}$$ = 0.64

Initial moment of inertia of the system,

$${{{\rm I}_1}}$$ = $${{M{{\left( {2L} \right)}^2}} \over {12}}$$

Final moment of inertia of the system,

I2 = $${{M{{\left( {2L} \right)}^2}} \over {12}}$$ + 2$$\left( {m{{\left( {{L \over 2}} \right)}^2}} \right)$$

$$ \therefore $$   $${{M{{\left( {2L} \right)}^2}} \over {12}}$$ = 0.64 $$\left[ {{{M{L^2}} \over 3} + {{m{L^2}} \over 2}} \right]$$

$$ \Rightarrow $$   $${{M{L^2}} \over {3 \times 0.64}}$$ = $${{M{L^2}} \over 3}$$ + $${{M{L^2}} \over 2}$$

$$ \Rightarrow $$   $${M \over {1.92}} - {M \over 3} = {m \over 2}$$

$$ \Rightarrow $$   $${{1.08M} \over {3 \times 1.92}}$$ = $${m \over 2}$$

$$ \Rightarrow $$   $${m \over M}$$ = $${{1.08 \times 2} \over {3 \times 1.92}}$$ = 0.37

Questions Asked from Waves

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

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Graduate Aptitude Test in Engineering

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

Medical

NEET