List of top Questions asked in JEE Main

A ball is projected vertically upward with an initial velocity of 50 ms–1 at t = 0 s. At t = 2 s, another ball is projected vertically upward with same velocity. 
At t = _____s, second ball will meet the first ball. (g = 10 ms–2)

In the given figure, the block of mass m is dropped from the point ‘A’. The expression for kinetic energy of block when it reaches point ‘B’ is

Fig. 
A block of mass M placed inside a box descends vertically with acceleration ‘a’.The block exerts a force equal to one-fourth of its weight on the floor of the box.
The value of ‘a’ will be
Water falls from a 40 m high dam at the rate of 9 × 104 kg per hour. Fifty percentage of gravitational potential energy can be converted into electrical energy. Using this hydro electric energy number of 100 W lamps, that can be lit, is :
(Take g = 10 ms–2)
In the wave equation $y=05 \sin \frac{2 \pi}{\lambda}(400 t-x) m$ the velocity of the wave will be :
Match List-I with List-II List-I List-II
Lis IList II
a.Ultraviolet raysi.Study crystal structure
b.Microwavesii.Greenhouse effect
c.Infrared wavesiii.Sterilizing surgical instrument
d.X-raysivRadar system

Choose the correct answer from the options given below :

Let K1 and K2 be the maximum kinetic energies of photo-electrons emitted when two monochromatic beams of wavelength λ1 and λ2, respectively are incident on a metallic surface. If λ1 = 3λ2 then:
A transverse wave is represented by \(y = 2sin(ωt – kx)\) \(cm\). The value of wavelength (in cm) for which the wave velocity becomes equal to the maximum particle velocity, will be

Match List-I with List-II.

                    List - IList - II
A.Television signal i.03 KHz 
B.Radio signalii.20 KHz
C.High Quality Musiciii.02 MHz
D.Human speechiv.06 MHz 

Choose the correct answer from the options given below:

 

A set of 20 tuning forks is arranged in a series of increasing frequencies. If each fork gives 4 beats with respect to the preceding fork and the frequency of the last fork is twice the frequency of the first, then the frequency of last fork is _______ Hz
Two travelling waves of equal amplitudes and equal frequencies move in opposite directions along a string. They interfere to produce a stationary wave whose equation is given by \(y = (10 cos \ \pi x\ sin \frac {2\pi t}{T})\) cm. The amplitude of the particle at \(x = \frac 43\) cm will be _______ cm.

A wire of length 30 cm, stretched between rigid supports, has it’s nth and (n + 1)th harmonics at 400 Hz and 450 Hz, respectively. If tension in the string is 2700 N, its linear mass density is _____ kg/m.

The frequency of echo will be _______ Hz if the train blowing a whistle of frequency 320 Hz is moving with a velocity of 36 km/h towards a hill from which an echo is heard by the train driver. Velocity of sound in air is 330 m/s.
The magnetic field of a plane electromagnetic wave is given by $\vec{ B }=2 \times 10^{-8} \sin \left(05 \times 10^3 x +15 \times 10^{11} t \right) \hat{ j } T$ The amplitude of the electric field would be
A plane of electromagnetic waves travels in a medium with a relative permeability of 1.61 and relative permittivity of 6.44. If the magnitude of magnetic intensity is 4.5 × 10–2 Am–1 at a point, what will be the approximate magnitude of electric field intensity?(Given: Permeability of free space μ0 = 4π × 10–7 NA–2, speed of light in vacuum c = 3 × 108 ms–1)

A baseband signal of 3.5 MHz frequency is modulated with a carrier signal of 3.5 GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal?

Match List I with List II

 List I List II
AFacsimileIStatic Document Image
BGuided media ChannelIILocal Broadcast Radio
CFrequency ModulationIIIRectangular wave
DDigital SingleIVOptical Fiber

The electric field in an electromagnetic wave is given by \(E = 56.5\ sin ω(t – \frac xc)\ NC^{–1}\). Find the intensity of the wave if it is propagating along x-axis in the free space. (Given \(∈_0 = 8.85 × 10^{–12} C^2N^{–1}m^{–2}\))

Which is the correct ascending order of wavelengths?
A sinusoidal wave y(t) = 40sin(10 × 106 πt) is amplitude modulated by another sinusoidal wave x(t) = 20sin(1000πt). The amplitude of minimum frequency component of modulated signal is:
An EM wave propagating in x-direction has a wavelength of 8 mm. The electric field vibrating y-direction has maximum magnitude of 60 Vm–1. Choose the correct equations for electric and magnetic field if the EM wave is propagating in vacuum:
The magnetic field of a plane electromagnetic wave is given by:
\(\vec B=2×10^{−8}sin⁡(0.5×10^3x+1.5×10^{11}t)\hat jT\).
The amplitude of the electric field would be
A radar sends an electromagnetic signal of electric field (E0) = 2.25 V/m and magnetic field (B0) = 1.5 × 10–8 T which strikes a target on line of sight at a distance of 3 km in a medium. After that, a part of signal (echo) reflects back towards the radar with same velocity and by same path. If the signal was transmitted at time t = 0 from radar, then after how much time echo will reach to the radar?
The TV transmission tower at a particular station has a height of 125 m. For doubling the coverage of its range, the height of the tower should be increased by
Sun light falls normally on a surface of area \(36 cm^2\) and exerts an average force of \(7.2 × 10^{–9} N\) within a time period of \(20 minutes\). Considering a case of complete absorption, the energy flux of incident light is