45406 + Interview Questions in Physics in Class 12

1.	Two relativistic particles move at right angles to each other in a laboratory frame of reference, one with the velocity v_1 and the other with the velocity v_2. Find their relative velocity.
Answer» Solution :The approach VELOCITY is defined by `vecV_(approach)=(dvecr_1)/(dt)-(dvecr_2)/(dt)=V_1-vecV_2` in the laboratory FRAME. So `V_(approach)=sqrt(v_1^2+v_2^2)` On the other hand, the RELATIVE velocity can be obtained by USING the velocity addition formula and has the componets `[-v_1, v_2sqrt(1-(v_1^2/c^2))]` so `V_r=sqrt(v_1^2+v_2^2-(v_1v_2^2)/(c^2))`

Discussion

2.	For maximum deviation D_(max) :
Answer» emergent ray must GRAZE the SURFACE (face) ncident ray must graze the surface `D_(max) = 90^@ + e - A` `D_(max) = 90^@ + i - A` ANSWER :C

Discussion

3.	State and explain Bohr's postulates forhydrogen atom.
Answer» Solution : Bohr gave following three postulates for hydrogen atom: 1. An electronrevolves round the NUCLEUS in certain specified circular ORBITS in which it does not radiate ENERGY. The centripetal force required for uniform circular motion in such a stationary orbit is provided by electrostatic force of attraction. Thus, `(m v_(n)^(2))/(r_(n)) = (1)/(4pi in_(0)) .(e^(2))/(r_(n)^(2))""......(i)` 2.Foran orbit to bestationary(ornon - radiating ) , theangularmomentum of theelectronmust bean integer multipleof `(h)/(2pi)`where h is thePlanck .s contant . Thus `L_(n) = m v_(n) r_(n) = (nh)/(2pi)"".......(ii)` 3. Wheneveran electron shift from oneof itsspecified non - radiatingorbitto anothersuchorbit , itemits /absorbs a photon whoseenergyis equalto theenergydifferencebetweenthe initial and final states . Thus . `E_(i)= E_(f)= HV = (hc)/(LAMBDA)""............(iii)`

Discussion

4.	An LED is constructed from a pn junction based on a certain semi-conducting material whose energy gap is 1.9 eV. Then the wavelength of the emitted light is
Answer» `9.1 XX 10^(-5)m` `6.5 xx 10^(-7)m` `1.6 xx 10^(-8)m` `2.9 xx 10^(-9)m` Solution :`E_(g)= (hc)/(lamda) rArr lamda= (hc)/(E_(g))= (6.63 xx 10^(-34) xx 3 xx 10^(8))/(1.9 xx 1.6 xx 10^(-19))= 6.5 xx 10^(-7)m`

Discussion

5.	A projective of 2kg was velocities 3mn/ sand 4m/s of two points during its flight in the uniform gravitational field of the earth. If these two velocities are bot to each other then the minimum KE of the particle during its flight is
Answer» Solution :`V_(1) cos alpha= V_(2) cos (90- alpha)` `3 cos alpha=4 sin alpha` `tan alpha=(3)/(4)` `KE_("min")=(1)/(2) mv_(1)^(2) cos^(2) alpha` `=(1)/(cancel7)xx cancel2xx3((4)/(5))^(2)=(9xx16)/(25)=5.76J`

Discussion

6.	A body accelerates from rest with a uniform acceleration a for time t. The uncertainty in a is 8% and the uncertainty in t is 4%. The uncertainty in speed is :
Answer» `32%` `12%` `8%` `20%` SOLUTION :`v=u+at+impliesv=0+atimpliesv=at.` `(Deltav)/(v)XX100=+-((Deltaa)/(a)xx100+(Deltat)/(t)xx100)` `=+-(8%+4%)=+-12%` So cannot choice is `(B)`.

Discussion

7.	(a) In what way is diffraction from each slit related to the interference pattern in a double-slit experiment? (b) Two wavelengths of sodium light 590 nm and 596 nm are used, in turn, to study the diffraction taking place at a single slit of aperture 2xx10^(-4)m. the distance between the slit and the screen is 1.5m. calculate the separation between the positions of first maxima of the diffraction pattern obtained in the two cases.
Answer» ANSWER :(B) `6.75xx10^(-5)`m

Discussion

8.	An object (O) is placed between two parallel plane mirror as shown in figure. Distance between the 4th image is
Answer» 16 m 32 m 8 m 64 m Solution :(B) DISTANCE between 4th images `I_(u)I_(u)^(')=2n(x+y)=2xx4[3+1]=32`

Discussion

9.	When a dimagnetic substance is brought near north or south poleof a bar magnet it is
Answer» attarcted by the poles REPELLED by the poles ATTRACTED by NORTH poleand repelled by south POLE repelled by north pole and attracted by south pole Answer :B

Discussion

10.	Material used for making permanent magnet has ...... and .......
Answer» HIGH RETENTIVITY, LOW coercivity low retentivity, high coercivity low retentivity, low coercivity high retentivity, high coercivity Answer :D

Discussion

11.	The deflection in a moving coil galvanometer is reduced to half,when it is shutned with a 40 ohm coil.The resistance of the galvanometer is :
Answer» 80 0hm 40 ohm 20 ohm 15 ohm Answer :B

Discussion

12.	The yeild of a nuclear reaction producing radionuclides may be described in two ways: either by the ratio omega of the numbers of nuclear reactions to the number of bombarding particles, or by the quantity k, the ratio of the activity of the formed radionuclide to the number of bombarding particles, Find: (a) the half-life of the formed radionuclide, assuming omega and k to be known: (b) the yield omega of the reaction Li^(7)(p,n)Be^(7) if after irradiation of a lithum target by a beam or protons(over t=2.0) hours and with =1.35.10^(8)dis//s and its half-life to T=53 days.
Answer» Solution :(a) Assuming of COURSE, that each reaction produces a radio nuclide of the same type, the decay constant `alpha` of the radionuclide is `k//W`. Hence `T=(In 2)/(LAMBDA)=(w)/(l)In2` (b) number of bombarding particles is : `(It)/(E )` (e = charge on proton.) Then the number of `Be^(7)` produced is : `(It)/( e)w`. If `lambda=` decay constant of `Be^(7)=(In2)/(T)`, then the acitvity is `A=(It)/(e )omega. (In2)/(T)` Hence `w=(eAT)/(It In 2)= 1.98xx10^(-3)`

Discussion

13.	By what percentage will the transmission range of a T.V. tower be affected when the height of the tower is increased by 21% ?
Answer» 0.1 0.2 0.3 0.4 Answer :A

Discussion

14.	Do all photos have same mass ? If no why ?
Answer» SOLUTION :Mass of a PHOTON = E/`C^2` = `(HV)/C^2` Different radiations have different frequencies. So, the photons will have different MASSES.

Discussion

15.	Assertion Energy of characteristic X-rays in more than the energy of continuous X-rays Reason Charactersitic X-rays are produced due to transition of electrons from higher energy states to lower energy states.
Answer» If both Assertion and Reason ar true and Reason is the correct EXPLANATION of Assertion. If both Assertion and Reason are true but Reason is not correct explanation of Assertion If Assertion is true by REASONIS false. If Assertion is false but Reason is true. SOLUTION :N//A

Discussion

16.	The nucleus " "_(10)^(23)Ne decays by beta^(-) emission. Write down the beta-decay equation and determine the maximum kinetic energy of the electrons emitted. Given that : m(" "_(10)^(23)Ne) = 22.994466 u, and m(" "_(11)^(23)Na) = 22.089770 u
Answer» Solution :Equation for `beta`-decay is `" "_(10)^(23)Ne (to) " "_(11)^23)Na + " "_(-1)^(0)e+ barnu +Q` Here, Q = energy released in `beta`-decay = maximum K.E. of the electron emitted and is given by `Q = [ m_(N) (" "_(10^(23)Ne) -{m_(N) (" "_(11)^(23)Na) +m_(e) }] U xx 931.5 MeV = [ {m(" "_(10)^(23)Ne) - 10m_(e) } - {m(" "_(11)^(23)Na) - 11m_(e) +m_(e)}]u xx 931.5 MeV = [ m(" "_(10)^(23)Ne)-m(" "_(11)^(23)Na)]u xx 931.5 MeV = (22.994466 u - 22.989770 u) xx 931.5 MeV = 0.004696 xx931.5 MeV = 4.374 MeV`

Discussion

17.	Assertion (A) : X - ray astronomy is possible only from satellites orbiting the earth. Reason (R ) : X - rays coming from extra terrestrial objects are scattered by the earth.s atmosphere.
Answer» If both assertion and rason are TRUE and the reason is the CORRECT EXPLANATION of the assertion. If both assertion and reason are true but reason is not the correct explanation of the assertion. If assertion is true but reason is false. If the assertion is false but reason is true. Solution :X-ray telescopes have extremely high VALUE of resolving power but these cannot be setup on the earth because X-rays are altogether scattered by earth.s atmosphere when X-rays coming from outer UNIVERSE pass through the atmosphere.

Discussion

18.	A block of metal weighs 2 kg is resting on a frictionless plane. It is struck by a jet releasing water 1 kg/s and at a speed of 5 m/s. The initial acceleration of the block will be ?
Answer» `2.5 m / s^2` `5 m / s^2` `10 m / s^2` `20 m / s^2` ANSWER :A

Discussion

19.	A 4 muF capacitor is charged by a 200 V supply. It is then disconnected from the supply, and isconnecled toanother uncharged 2 muf capacitor. How much electrostatic energy of the first capacilor is lost in the form of heat and electromagnetic radiation ?
Answer» Solution :Energy stored in capacitor of 4 `mu`F initially . `U_(i)=(1)/(2) CV^(2)= (1)/(2) xx4xx10^(-6)xx(200)^(2)` `U_(i) = 8xx10^(-2) J` CHARGE on capacitor of `4 muF` `Q =CV = 4xx10^(-6) xx200` `:. Q = 8xx10^(-4)` C Potential of combination of CAPACITORS `4muF` and `2 muF` `V_(1) = ("Total charge")/("Total CAPACITANCE") = (0+8xx10^(-4))/((4+2)xx10^(-6))` `:.V_(1)=(8xx10^(-4))/(6xx10^(-6))=(800)/(6) =(400)/(3) V ` Final electrostatic energy of combination `U_(f) = (1)/(2) (C_(1)+C_(2))V_(1)^(2)` `=(1)/(2)(4+2)xx10^(-6)xx((400)/(3))^(2)` `=(1)/(2)xx(6xx10^(-6)xx16xx10^(4))/(9)` `:. U_(f) =(16)/(3) xx10^(-2)J` `= 5.33xx1^(-2) J` Hence amount of electrostatic energy lost by capacitor of `4 muF ` `DeltaU = U_(i) -U_(f)` `= (8-5.33) xx10^(-2) J` `= 2.67xx10^(-2) J`

Discussion

20.	Why do we use very thin gold foil in Rutherford's alpha-particle experiment ?
Answer» Solution :In thick FOIL, the ENTIRE K.E. of `alpha -PARTICLE` will be absorbed and so a `alpha-particle` will not be able to penetrate through the COIL.

Discussion

21.	What is the second advice?
Answer» ONE should HOPE for the best One should not anticipate evils Learn NEVER to conceive a prejudice against others None of the above Answer :B

Discussion

22.	A parallel beam of light falls on a solid tranparent sphere. Q. If however thin beam is focussed at A, then find the refractive index of the sphere,
Answer» 1.5 1.7 `2.0` 2.5 Solution : `(mu)/(y)-(1)/(OO)=(mu-1)/(R)rArr(muR)/(mu-1)` If beam is focussed at A, than ` y=2R` `rArr 2R=(muR)/(mu-1)=mu=2` The above is VALID for paraxial rays, HENCE beam should be thin. If `mugt2` , then `ylt2R` , hence beam can be focussed before A. For thin beam to be focussed at A, `y=R`. `rArrR=(muR)/(mu-1)rArr mu=oo`(not possible)

Discussion

23.	Electron cannot be a part of nucleus but protons can be. Why?
Answer» SOLUTION :This is because de Broglie wavelength ASSOCIATED with electrons is larger than the SIZE of nucleus. And the de Broglie wavelength associated with protons is SMALLER than the size of nucleus.

Discussion

24.	If M is the mass of a nucleus and A is its mass number, then (M -A)/(M) is called its
Answer» BINDING energy Fermi energy mass defect packing fraction Solution :N//A

Discussion

25.	(A) : The resultant magnetic field on the axial point of circular loop is due to the axial component of field. (R) : In circular loop of wire, perpendicular components of magnetic field at some distance from centre of loop summed over the whole loop, the result is zero.
Answer» Both 'A' and 'R' are true and 'R' is the correct EXPLANATION of 'A'. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A' 'A' is true and 'R' is FALSE 'A' is false and 'R' is false Answer :A

Discussion

26.	A convex lens is placed some where between an object and a screen which are separated by48 cm. If the numerical value of magnification produced by the lens is 3, what is the focal length of lens?
Answer» 6cm 12cm 24cm 9cm Answer :D

Discussion

27.	In a compound microscope, maximum magnification is obtained when the final image
Answer» is formed at infinity is formed at the least DISTANCE of DISTRICT vision coincies with the object coincides with the OBJECTIVE lens Answer :B

Discussion

28.	Write down the advantages and limitations of amplitude modulation (AM)? Advantages of AM
Answer» Solution :(i) Easy transmission and reception (ii) Lesser bandwidth REQUIREMENTS (III) Low COST Limitations of AM (i) Noise level is high (ii) Low EFFICIENCY (iii) Small operating range

Discussion

29.	Who is Jill ?
Answer» JACK's wife Jack's sister Jack's mother None of the above Answer :A

Discussion

30.	A 100 W bulb is connected to an AC source of 220 V, 50 HZ . Then the current flowing through the bulb is
Answer» `5/11A` `1/2A` 2A `3/4A` SOLUTION :`I=P/V=100/220=5/11A`

Discussion

31.	In Rutherford atomic model central part of atom where whole positive charge of atom is concentrated is called ......
Answer» CENTRE of atom centre of MASS of atom NUCLEUS sphere SOLUTION :nucleus

Discussion

32.	a. The far point of a myopic person is 80cm in front of the eye. What is the power of the lens required to enable him to see very distant object clearly ? b. In what way does the corrective lens help the above person ? Does the lens magnify very distantobjects? Explain carefully. c.The above person profers to remove his spectacles while reading a book Explain why.
Answer» Solution :Solving we find that the person should use a concave lens of focal length= -80 cm, i.e., of power = - 1.25 dioptres. b.No. The concave lens, in fact, reduces the SIZE of the OBJECT, but the angle subtended by the distant object at the eye is the same as the angle subtended by the image (at the far point ) at the eye. THe eye is able to see distant objects not because the corrective lens magnifies the object, but because it brings the object (i.e., it produces virtual image of the object ) at the far point of the eye which then can be FOCUSSED by the eye-lens on the retina. c. The myopic person may have a normal near point, i.e, about 25 cm (or even LESS ) . In order to read a book with the spectacles , such a person must keep the book at a distance not CLOSER than 25 cm. The angular size of the book (or its image ) at the greater distance is evidently less than the angular size when the book is placed at 25 cm and so spectacles are needed Hence, the person prefers to remove the spectacles while reading .

Discussion

33.	Protential energy of an ideal spring , when stretched by 1 cm is U. Spring is now cut in two equal parts and connected in parallei. If the new combination of Spring is compressed by 2 cm, then potential energy stored is
Answer» 2U 8U 16U 4U Answer :a

Discussion

34.	When electron beam passes through an electric field,they gain kinetic energy. If the same beam passes through magnetic field, then
Answer» Their ENERGY increases Their MOMENTUM increases Their POTENTIAL energy increases Energy and momentum both REMAINS unchanged Answer :D

Discussion

35.	Two identical pendulums A and B are suspended from the same point. Both are given positive charge, with A having more charge than B. They diverge and reach equilibrium with the suspension of A and B making angles theta_1 and theta_2 with the vertical respectively.
Answer» `theta_1 GT theta_2` `theta_1 LT theta_2` `theta_1 = theta_2` The tension in A is GREATER than that in B ANSWER :C

Discussion

36.	The greatest acceleration or deceleration that a train may have is a. The minimum time in which the train can get from one station to the next at a distance s is:
Answer» `SQRT((s)/(a))` `sqrt((2S)/(a))` `2sqrt((s/a))` `1/2 sqrt((s)/(a))` SOLUTION :Here let the ACCELERATION and retardaion take placefor `t/2` sec each. Then `S=(1)/(2)((at^(2))/(2))xxt` or `(at^(2))/(4)=S` or `t=2sqrt((S)/(a))`

Discussion

37.	Consider a semicircular ring with mass m and radius R as shown in figure. Statement-1: The moment of inertia of semi - circular ring about an axis passing through A and perpendicular to plane is 2mR^(2) Statement-2: According to parallel axis theorem: I_(A)=1_(cm)+mR^(2)
Answer» STATEMENT-1 is TRUE, statement-2 is true and statement-2 is correct explanation for statement-1. Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1. Statement-1 is true, statement-2 is FALSE. Statement -1 is false, statement -2 is true. Solution :`I=(2mR^(2)+2mR^(2))/2` (due to SYMMETRY)

Discussion

38.	A charge q is accelerated through a potential difference V . It is then passed normally through a uniform magnetic field, where it moves in a circle of radius r. Then potential difference required to move it in a circle of radius 2 r is
Answer» 2V 4V 1V 3V Solution :RADIUS of CIRCULAR path : r = `sqrt(2mqV)/(qB)` `rpropsqrtV` where B is constant or `Vpropr^(2)` `V_(2)/V_(1)=(r_(2)/r_(1))^(2)` `V_(2)/V=((2r)/r)^(2)4rArrV_(2)=4V`

Discussion

39.	Two particles which are initially at rest move towards each other under the action of their mutual attraction. If their speeds are v and 2v at any instant, then the speed of center of mass of the system is,
Answer» 0 V 3V 1.5 V Solution :As no external force acts on the SYSTEM so the CENTRE of mass will REMAIN at REST.

Discussion

40.	A ferfectly black body is one which absorbs radiation of
Answer» all wavelengths large wavelengths small wavelengths infrared wavelengths Answer :A

Discussion

41.	Focal length of thin lens ......
Answer» decreases with increase in REFRACTIVE index. increases with increase in refractive index. doesn.t change with refractive index. NONE of these Solution :For LENS, From `1/f=(N-1)[1/R_1-1/R_2],1/f prop n`

Discussion

42.	In the magnetic meridian of a certain place, the horizontal component of the earth's magnetic field is 0.1414 G and the dip angle is 45°. What is the magnetic field of the earth at this location ?
Answer» SOLUTION :`B_E= 0.2 G`

Discussion

43.	What is the kind of pain and ache that the poet feels?
Answer» LOSING her mother heart attack headache children SCREAMING at her Answer :A

Discussion

44.	A spherical mirror is held in water , its focal length :
Answer» INCREASES DECREASES remains same may increases or decreases for convex or concave mirror Answer :C

Discussion

45.	A transparent cube of 15 cm edge contains a small air bubble. Its apparent depth when viewed through one face is 6 cm and when viewed through the opposite face is 4 cm. Then the refractive index of the material of the cube is,
Answer» 2 2.5 1.6 1.5 Answer :D

Discussion

46.	(a) A long straight wire carries a current I into the plane of the figure. AB is a straight line in the plane of the figure subtending an angle thetae point of intersection of the wire with the plane. Find (by integration) the line integral of magnetic field along the line AB. (b) In the last problem the straight line AB is replaced with a curved line AB as shown in figure. Can you calculate the line integral of magnetic field B along this curved line? If yes, what is its value?
Answer» Answer :`(a)theta/(2pi)mu_(0)I` (b)YES,LINE INTEGRAL is `theta/(2pi)mu_(0)I`

Discussion

47.	A uniform but time varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of paper as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region.
Answer» is zero decreases as `(1)/(r )` increases as r decreases as `(1)/(r^(2))` Solution :`oint VEC(E ).vec(dl)=\|(-d PHI)/(dt)\|=(d)/(dt)(pi a^(2)B)` or`E2 pi r=pi a^(2)\|(dB)/(dt)\|therefore E=(a^(2))/(2r)\|(dB)/(dt)\| therefore E prop (1)/(r )`.

Discussion

48.	If the total charge enclosed by a surface is zero, does it imply that the electric field everywhere on the surface is zero ? Conversely, if the electric field everywhere on a surface is zero, does it imply that net charge inside is zero.
Answer» Solution :Electric flux `phi = oint_(S) vecE. DVECS =q/(epsilon_(0))` In left side of equation, `vecE` is electric FIELD on the SURFACE by charges inside and OUTSIDE the surface. But, in right side of equation, q is the charge enclosed by the surface. It means, if q = 0, then may `E ne 0`because there may be E DUE to charges outside the surface.But, if E = 0, then q = 0. (Charge enclosed by surface)

Discussion

49.	If the number density of molecule of an ideal gas becomes 4 time then its mean free path becomes
Answer» HALF of its INITIAL value Double of its initial value Four TIME of its initial value One FOURTH of its initial value Answer :D

Discussion

50.	A particle of charge 'q' and mass 'm' moves in a circular orbit of radius 'r' with angular speed 'omega' . The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on
Answer» `OMEGA` and Q `omega`, q and m q and m `omega` and m Answer :C

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Two relativistic particles move at right angles to each other in a laboratory frame of reference, one with the velocity v_1 and the other with the velocity v_2. Find their relative velocity.

For maximum deviation D_(max) :

State and explain Bohr's postulates forhydrogen atom.

An LED is constructed from a pn junction based on a certain semi-conducting material whose energy gap is 1.9 eV. Then the wavelength of the emitted light is

A projective of 2kg was velocities 3mn/ sand 4m/s of two points during its flight in the uniform gravitational field of the earth. If these two velocities are bot to each other then the minimum KE of the particle during its flight is

A body accelerates from rest with a uniform acceleration a for time t. The uncertainty in a is 8% and the uncertainty in t is 4%. The uncertainty in speed is :

An object (O) is placed between two parallel plane mirror as shown in figure. Distance between the 4th image is

When a dimagnetic substance is brought near north or south poleof a bar magnet it is

Material used for making permanent magnet has ...... and .......

The deflection in a moving coil galvanometer is reduced to half,when it is shutned with a 40 ohm coil.The resistance of the galvanometer is :

By what percentage will the transmission range of a T.V. tower be affected when the height of the tower is increased by 21% ?

Do all photos have same mass ? If no why ?

Assertion Energy of characteristic X-rays in more than the energy of continuous X-rays Reason Charactersitic X-rays are produced due to transition of electrons from higher energy states to lower energy states.

The nucleus " "_(10)^(23)Ne decays by beta^(-) emission. Write down the beta-decay equation and determine the maximum kinetic energy of the electrons emitted. Given that : m(" "_(10)^(23)Ne) = 22.994466 u, and m(" "_(11)^(23)Na) = 22.089770 u

Assertion (A) : X - ray astronomy is possible only from satellites orbiting the earth. Reason (R ) : X - rays coming from extra terrestrial objects are scattered by the earth.s atmosphere.

A block of metal weighs 2 kg is resting on a frictionless plane. It is struck by a jet releasing water 1 kg/s and at a speed of 5 m/s. The initial acceleration of the block will be ?

A 4 muF capacitor is charged by a 200 V supply. It is then disconnected from the supply, and isconnecled toanother uncharged 2 muf capacitor. How much electrostatic energy of the first capacilor is lost in the form of heat and electromagnetic radiation ?

Why do we use very thin gold foil in Rutherford's alpha-particle experiment ?

What is the second advice?

A parallel beam of light falls on a solid tranparent sphere. Q. If however thin beam is focussed at A, then find the refractive index of the sphere,

Electron cannot be a part of nucleus but protons can be. Why?

If M is the mass of a nucleus and A is its mass number, then (M -A)/(M) is called its

(A) : The resultant magnetic field on the axial point of circular loop is due to the axial component of field. (R) : In circular loop of wire, perpendicular components of magnetic field at some distance from centre of loop summed over the whole loop, the result is zero.

A convex lens is placed some where between an object and a screen which are separated by48 cm. If the numerical value of magnification produced by the lens is 3, what is the focal length of lens?

In a compound microscope, maximum magnification is obtained when the final image

Write down the advantages and limitations of amplitude modulation (AM)? Advantages of AM

Who is Jill ?

A 100 W bulb is connected to an AC source of 220 V, 50 HZ . Then the current flowing through the bulb is

In Rutherford atomic model central part of atom where whole positive charge of atom is concentrated is called ......

Protential energy of an ideal spring , when stretched by 1 cm is U. Spring is now cut in two equal parts and connected in parallei. If the new combination of Spring is compressed by 2 cm, then potential energy stored is

When electron beam passes through an electric field,they gain kinetic energy. If the same beam passes through magnetic field, then

Two identical pendulums A and B are suspended from the same point. Both are given positive charge, with A having more charge than B. They diverge and reach equilibrium with the suspension of A and B making angles theta_1 and theta_2 with the vertical respectively.

The greatest acceleration or deceleration that a train may have is a. The minimum time in which the train can get from one station to the next at a distance s is:

Consider a semicircular ring with mass m and radius R as shown in figure. Statement-1: The moment of inertia of semi - circular ring about an axis passing through A and perpendicular to plane is 2mR^(2) Statement-2: According to parallel axis theorem: I_(A)=1_(cm)+mR^(2)

A charge q is accelerated through a potential difference V . It is then passed normally through a uniform magnetic field, where it moves in a circle of radius r. Then potential difference required to move it in a circle of radius 2 r is

Two particles which are initially at rest move towards each other under the action of their mutual attraction. If their speeds are v and 2v at any instant, then the speed of center of mass of the system is,

A ferfectly black body is one which absorbs radiation of

Focal length of thin lens ......

In the magnetic meridian of a certain place, the horizontal component of the earth's magnetic field is 0.1414 G and the dip angle is 45°. What is the magnetic field of the earth at this location ?

What is the kind of pain and ache that the poet feels?

A spherical mirror is held in water , its focal length :

A transparent cube of 15 cm edge contains a small air bubble. Its apparent depth when viewed through one face is 6 cm and when viewed through the opposite face is 4 cm. Then the refractive index of the material of the cube is,

A uniform but time varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of paper as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region.

If the total charge enclosed by a surface is zero, does it imply that the electric field everywhere on the surface is zero ? Conversely, if the electric field everywhere on a surface is zero, does it imply that net charge inside is zero.

If the number density of molecule of an ideal gas becomes 4 time then its mean free path becomes

A particle of charge 'q' and mass 'm' moves in a circular orbit of radius 'r' with angular speed 'omega' . The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on