List of top Questions asked in JEE Main

A lens having refractive index 1.6 has focal length of 12 cm, when it is in air. Find the focal length of the lens when it is placed in water. (Take refractive index of water as 1.28)
Two thin convex lenses of focal lengths 30 cm and 10 cm are placed coaxially, 10 cm apart. The power of this combination is:

In the following circuit, the reading of the ammeter will be: (Take Zener breakdown voltage = 4 V)

Two projectiles are fired from the ground with the same initial speeds from the same point at angles $ (45^\circ + \alpha) $ and $ (45^\circ - \alpha) $ with the horizontal direction. The ratio of their times of flights is:

Match the List-I with List-II.

Choose the correct answer from the options given below:

A cubic block of mass $ m $ is sliding down on an inclined plane at $ 60^\circ $ with an acceleration of $ \frac{g}{2} $, the value of coefficient of kinetic friction is:
In a hydrogen-like ion, the energy difference between the 2nd excitation energy state and ground is 108.8 eV. The atomic number of the ion is:
For a hydrogen atom, the ratio of the largest wavelength of the Lyman series to that of the Balmer series is:

A particle of charge $ q $, mass $ m $, and kinetic energy $ E $ enters in a magnetic field perpendicular to its velocity and undergoes a circular arc of radius $ r $. Which of the following curves represents the variation of $ r $ with $ E $?

An object of mass 1000 g experiences a time-dependent force $ \vec{F} = (2t \hat{i} + 3t^2 \hat{j}) \, \text{N} $. The power generated by the force at time $ t $ is:
Two wires A and B are made of the same material, having the ratio of lengths $ \frac{L_A}{L_B} = \frac{1}{3} $ and their diameters ratio $ \frac{d_A}{d_B} = 2 $. If both the wires are stretched using the same force, what would be the ratio of their respective elongations?

Two charges $ q_1 $ and $ q_2 $ are separated by a distance of 30 cm. A third charge $ q_3 $ initially at C as shown in the figure, is moved along the circular path of radius 40 cm from C to D. If the difference in potential energy due to the movement of $ q_3 $ from C to D is given by $ \frac{q_3 K}{4 \pi \epsilon_0} $, the value of $ K $ is:

A, B and C are disc, solid sphere and spherical shell respectively with the same radii and masses. These masses are placed as shown in the figure.

The moment of inertia of the given system about PQ is $ \frac{x}{15} I $, where $ I $ is the moment of inertia of the disc about its diameter. The value of $ x $ is:

For the AC circuit shown in the figure, $ R = 100 \, \text{k}\Omega $ and $ C = 100 \, \text{pF} $, and the phase difference between $ V_{\text{in}} $ and $ (V_B - V_A) $ is 90°. The input signal frequency is $ 10^x $ rad/sec, where $ x $ is:

A container contains a liquid with refractive index of 1.2 up to a height of 60 cm and another liquid having refractive index 1.6 is added to height $ H $ above the first liquid. If viewed from above, the apparent shift in the position of the bottom of the container is 40 cm. The value of $ H $ is ___ cm.
A wire of length 10 cm and diameter 0.5 mm is used in a bulb. The temperature of the wire is 1727°C and power radiated by the wire is 94.2 W. Its emissivity is $ \frac{x}{8} $, where $ x = \ldots $

An ideal gas has undergone through the cyclic process as shown in the figure. Work done by the gas in the entire cycle is _____ $ \times 10^{-1} $ J. (Take $ \pi = 3.14 $)

Given below are two statements:
Statement I: Ozonolysis followed by treatment with Zn, H$_2$O of cis-2-butene gives ethanal.
Statement II: The product obtained by ozonolysis followed by treatment with Zn, H$_2$O of 3, 6-dimethyloct-4-ene has no chiral carbon atom.
In the light of the above statements, choose the correct answer from the options given below.

Which of the following amine(s) show(s) positive carbamylamine test?

Reaction A(g) → 2B(g) + C(g) is a first-order reaction. It was started with pure A.
The following table shows the pressure of the system at different times: 

Which of the following options is incorrect?

Total enthalpy change for freezing of 1 mol water at 10°C to ice at -10°C is ______ (Given: $ \Delta_{\text{fus}}H = x \, \text{kJ/mol} $, $ C_p[\text{H}_2\text{O}(l)] = y \, \text{J mol}^{-1} \text{K}^{-1} $, and $ C_p[\text{H}_2\text{O}(s)] = z \, \text{J mol}^{-1} \text{K}^{-1} $)
An aqueous solution of HCl with pH 1.0 is diluted by adding equal volume of water (ignoring dissociation of water). The pH of HCl solution would be: $ \text{(Given log 2 = 0.30)} $

Given below are two statements: 
Statement I: Dimethyl ether is completely soluble in water. However, diethyl ether is soluble in water to a very small extent.
Statement II: Sodium metal can be used to dry diethyl ether and not ethyl alcohol.
In the light of the given statements, choose the correct answer from the options given below:


Which of the following statements are correct, if the threshold frequency of caesium is $ 5.16 \times 10^{14} \, \text{Hz} $?

Which of the following is the correct IUPAC name of the given organic compound (X)? The structure of compound $ X $ is as follows: $ \text{H}_3\text{C} - \text{CH}_3 - \text{CH} = \text{CH} - \text{H} - \text{Br} $