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Questions >> JEEMAIN and NEET >> Physics

Physics

Find the amplitude of the electric field in a parallel beam of light of intensity $2\: W/m^2$

asked Mar 1, 2014 by thanvigandhi_1

1 answer

The electric field in an electromagnetic wave is given by $E = 50N/C\: \sin \omega (t-x/c)$. Find the energy contained in a cylinder of cross-section $10cm^2$ and length 50 cm along the x-axis.

asked Mar 1, 2014 by thanvigandhi_1

1 answer

The average energy flux of sunlight is $1\: kW/m^2$. This energy is falling normally on the plate surface of area $10\: cm^2$ which completely absorbs the energy. How much force is exerted on the plate if it is exposed to sunlight for 20 minutes?

asked Mar 1, 2014 by thanvigandhi_1

1 answer

The magnetic field in a plane electromagnetic wave is given by $B = 100\mu T \sin [(2 \times10^{15}s^{-1}) (t-x/c)]$. Calculate the average energy density corresponding to the electric field.

asked Mar 1, 2014 by thanvigandhi_1

1 answer

A light beam travelling in the x-direction is described by the electric field $E_y = 300 \: V/m \: \sin \omega\: (t – x/c)$. An electron is constrained to move along the y-direction with a speed of $2 \times 10^7 m/s$. Find the maximum magnetic force on the electron

asked Mar 1, 2014 by thanvigandhi_1

1 answer

A plane sinusoidal linearly polarized electromagnetic wave of wavelength $ 5 \times 10^{-7}m$ travels in vacuum in the direction of $x$ - axis. The average intensity of the wave per unit area is $0.1\: W/m^2$ and the plane of vibration of electric field is parallel to $y$ - axis. The equations describing the electric and magnetic field of this wave is

asked Mar 1, 2014 by thanvigandhi_1

1 answer

A $60W$ monochromatic point source radiating equally in all directions in vacuum is being monitored at a distance of $2m$. Determine the amplitude if the electric field.

asked Mar 1, 2014 by thanvigandhi_1

1 answer

A laser emits a beam of light of $2mm$ diameter. If the power of beam is $10mW$, the intensity of the beam of light is

asked Feb 28, 2014 by thanvigandhi_1

1 answer

We can establish an instantaneous displacement current of $1\: A$ in the space between the two plates of a $1\: \mu\: F$ parallel plate capacitor by varying voltage at the rate of

asked Feb 28, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor has circular plates, each of radius $5\: cm$. It is being charged so that electric field in the gap between its plates rises steadily at the rate of $10^{12}V/ms$. What is the displacement current?

asked Feb 28, 2014 by thanvigandhi_1

1 answer

A radio wave of intensity $I$ is reflected by a surface. The intensity $ (I)$, if pressure exerted on the surface is $2 \times 10^{-8} N/m^2$ , will be:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

What is order of energy of X-rays $(E_X)$, radio waves $(E_R)$, and micro waves $(E_M)$?

asked Feb 28, 2014 by thanvigandhi_1

1 answer

A TV tower has a height of $100\: m$. The area covered by the TV broadcast, if radius of the earth is $6400\: km$, will be:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

Some radio waves of frequency of about $1.5 \times 10^9$ Hz were received by a radio-telescope from distant star. If the speed of the waves is $3 \times 10^5 \: km/s$, then the wave- length of the wave will be:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

An object is placed at some distance from a radio station. If the interval between transmission and reception of pulses is $2.66 \times 10^{-2}\: sec$, then the distance is:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

The speed of light in air, if an electromagnetic wave is travelling in air whose dielectric constant is $k = 1.006$, will be :

asked Feb 28, 2014 by thanvigandhi_1

1 answer

The energy of photon of electromagnetic radiation of wavelength = $2000\: A^{\circ}$ is:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

The AM radio wave bends appreciably round the corners of a $1m \times 1m$ board but the FM wave only negligibly bands. If the average wavelength of the AM and FM waves are $ \lambda_a$ and $\lambda_f$ , then

asked Feb 28, 2014 by thanvigandhi_1

1 answer

If an electromagnetic wave of frequency $v = 3.0\: MHz$ passes from vacuum into a dielectric medium with permittivity $e = 4.0$ then

asked Feb 28, 2014 by thanvigandhi_1

1 answer

The displacement $y$ of a particle in a medium can be expressed as $y = 10^{-6} \sin \bigg(100t + 20x + \large\frac{\pi}{4}\bigg)m$, where $t$ is in second and $x$ is in metre. The speed of the wave is

asked Feb 28, 2014 by thanvigandhi_1

1 answer

An uniform electric field and an uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then

asked Feb 28, 2014 by thanvigandhi_1

1 answer

In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a

asked Feb 28, 2014 by thanvigandhi_1

1 answer

A wave travelling along the $x$ - axis is described by the equation $y(x,t) = 0.005\: \cos(\alpha x - \beta t)$. If the wavelength and time period of the wave are $0.08 \: m $ and $2\: s$, respectively, then $ \alpha$ and $ \beta$ in appropriate units are

asked Feb 28, 2014 by thanvigandhi_1

1 answer

If a source of power $4\: kW$ produce $10^{20}$photons/s, the radiation belongs to a part of spectrum called

asked Feb 28, 2014 by thanvigandhi_1

1 answer

The time period of a charged simple pendulum in an electric field is:

asked Feb 28, 2014 by thanvigandhi_1

1 answer

If activity of a radioactive substance's $\;A_{1}\;$ at time $\;t_{1}\;$ & $\;A_{2}\;$ at time $\;t_{2}\;$ $\;(> t_{1})\;$ . Its decay constant is $\;\lambda\;$ . Then

asked Feb 28, 2014 by yamini.v

1 answer

If ratio of molecular masses of two radioactive substances is $\;\large\frac{1}{2}\;$ and ratio of decay constant is $\;\large\frac{5}{3}\;$ . Then ratio of their initial activity per mole will be

asked Feb 28, 2014 by yamini.v

1 answer

x atoms of a radioactive element emit y beta particles per second . Then the decay constant of element is (in $\;s^{-1}$) .

asked Feb 28, 2014 by yamini.v

1 answer

The equation : \[\] $\;4 _{1}^{1}H \to _{2}^{4}He^{2+}+2e^{-}+32 MeV\;$ represents

asked Feb 28, 2014 by yamini.v

1 answer

Which of the following is correct statement ?

asked Feb 28, 2014 by yamini.v

1 answer

$\;^{22}Ne\;$ Nucleus after absorbing energy , decays into two $\;\alpha-\;$ particles and an unknown nucleus . The unknown nucleus is

asked Feb 28, 2014 by yamini.v

1 answer

The half -life period of a radioactive element A is same as mean life of another radioactive element B . Initially both of them have same number of atoms

asked Feb 28, 2014 by yamini.v

1 answer

A nucleus with mass number 200 initially at rest emits and $\;\alpha-\;$ particle . If Q value of reaction is 4.2MeV .Then kinetic energy of $\;\alpha-\;$ particle will be

asked Feb 28, 2014 by yamini.v

1 answer

Two radioactive materials A & B have decay constants 12X & X respectively . If initially they have same no.of nuclei , then ratio of no. of nuclei of A to B will be $\;\large\frac{1}{e}\;$ after a time

asked Feb 27, 2014 by yamini.v

1 answer

Half life of a radioactive substance A is 4 days . The probability that a nucleus will decay in two half-lives is :

asked Feb 27, 2014 by yamini.v

1 answer

If a star can convert all He nuclei completely into oxygen nuclei . The energy released per oxygen nuclei is . [Mass of nucleus He is 4.0026 amu & mass of oxygen nucleus is 15.9994]

asked Feb 27, 2014 by yamini.v

1 answer

A star initially has $\;10^{4}\;$ deuterons . It produces energy via the process \[\] $\;_{1}H^{2}+_{1}H^{2} \to _{1}H^{3}+P\;$ and \[\] $\;_{1}H^{2}+_{1}H^{3} \to _{2}He^{4}+n\;$\[\] If average power radiated by star is $\;10^{16} W\;$ the deutron supply of star is exhausted in a time of order of

asked Feb 27, 2014 by yamini.v

1 answer

The binding energy of two nuclei A & B are X & Y . Two atoms of A fuse to give one atom of B an energy P is released . Then

asked Feb 27, 2014 by yamini.v

1 answer

The half life of radioactive radon is 3.8 days . The time , at end of which $\;\large\frac{1}{20}^{th}\;$ of radon sample will remain undecayed is

asked Feb 27, 2014 by yamini.v

1 answer

The displacement $y$ of a wave travelling in the $x$ - direction is $y = 10^{-4} \sin(600t – 2x + \large\frac{\pi}{3})m$, where, $x$ is in $m$ and $t$ is in $s$. The speed of the wave motion in $m/s$ is

asked Feb 27, 2014 by thanvigandhi_1

1 answer

An electric line of force in the $xy$ plane is given by equation $x^2+y^2=1$. A particle with unit positive charge, initially at rest at the point $x = 1, y = 0$ in the $xy$ plane

asked Feb 27, 2014 by thanvigandhi_1

1 answer

If $c$ is the speed of electromagnetic waves in vacuum, their speed in a medium of dielectric constant $K$ and relative permeability $ \mu_r$ is

asked Feb 27, 2014 by thanvigandhi_1

1 answer

A beam of light travelling along $ x$ - axis is described by the electric field $E_y = (600 V/m) \sin \omega (t - x/c)$ then maximum magnetic force on a charge $q = 2e$, moving along $y$ - axis with a speed of $3.0 \times 10^7m/s$ is $(e = 1.6 \times 10^{-19} C)$

asked Feb 27, 2014 by thanvigandhi_1

1 answer

About 5% of the power of a $100\: W$ light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of $10\: m$ from the bulb?

asked Feb 27, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor of area $50\: cm^2$ and plate separation $3\: mm$ is charged initially to $80\: \mu C$. Due to a radioactive source nearby, the medium between the plates gets slightly conducting and the plate loses charge initially at the rate of $1.5 \times 10^{-8}C/s$. What is the magnitude and direction of displacement current?

asked Feb 27, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor with plate area $A$ and separation $d$ between the plates is charged by a constant current $i$. Consider a plane surface of area $A/4$ parallel to the plates and drawn symmetrically between the plates. Calculate the displacement current through this area.

asked Feb 27, 2014 by thanvigandhi_1

1 answer

Find the energy of a photon in electron volt of microwaves having wavelength $3mm.(1\: eV = 1.6 \times 10^{-19}J)$

asked Feb 27, 2014 by thanvigandhi_1

1 answer

Light with an energy flux of $18\: W/cm^2$ surface has an area of $ 20\: cm^2$ falls on a non-reflecting surface at normal incidence. If the , the average force exerted on the surface during a $30$ minute time span is

asked Feb 27, 2014 by thanvigandhi_1

1 answer

The magnetic field in a plane electromagnetic wave is given by $B_y= 2 \times 10^{-7} \: \sin (0.5\times10^3x+1.5\times10^{11}t)T$ The wavelength and frequency of the wave are

asked Feb 27, 2014 by thanvigandhi_1

1 answer

A plane electromagnetic wave of frequency $25\: MHz$ travels in free space along the $x$ - direction. At a particular point in space and time, $E= 6.3 \: jV/m$. What is B at this point?

asked Feb 27, 2014 by thanvigandhi_1

1 answer

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