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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
From the standpoint of the corpuscular theory demostrate that the momentum transferred by a beam of parallel light rays per unit time does not depend on its spectral composition but depends only on the enegry flux Theta_(e). |
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Answer» Solution :The statement made in the QUESTION is not always correct. However it is correct in certain cases, for example, when light is incident on a perfect reflector or perfect absorber. Consider the former case. If light is incident at an angle `theta` and reflectef at the angle `theta`, then momentum transfered by each photon is `2(hv)/(c ) cos theta` If there are `n(v)dv` PHOTONS is FREQUENCY interval `(v,v+dv)`, then totao momentum transfered is `underset(0)OVERSET(oo)int 2N(v)(hv)/(c ) costheta dv` `= (2Phi_(e))/(c ) costheta` 
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| 3. |
A ray of light strikes a silvered surface inclined to another one at an angle of 90^(@). Then the reflected ray will turn through |
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Answer» `0^(@)` `:. /_r=0^(@)` i.e. the reflected RAY WOULD retrace its path turning through `180^(@)`. Mirror `M_(2)` has no effect. |
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| 4. |
When a number of capacitors are connected in parallel, the equivalent capacitance is equal to_____of their individual capacitor. |
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| 5. |
An a.c. source of variable angular frequency o is connected to an LCR series circuit. Which one of the following graphs correctly represents variation of impedance Zof a.c. circuit with angular frequency omega? |
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| 7. |
A whistle is whirled in a circle of radius one metre and traverses the sircular path twice per second. An observer is situated outside the circle but in its plane. If the velocity of sound is 332 m/s, then the interval between the highest and the lowest observed pitch is : |
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Answer» `332:1` |
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| 8. |
Two inductors each of inductance L are connected in parallel. One more inductor of value 5 mH is connected in series of this configuration then the effective inductance is 15 mH. The value of L is .......... mH. |
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Answer» 10 Now , `L/2 +5 =15` `therefore L/2 =10 therefore` L=20 mH. |
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| 9. |
Define electronVolt and convert it into Joule unit. |
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Answer» Solution :If an electron with charge q =e=`1.6xx10^(-19)` C is accelerated by a potential difference of 1 volt it would gain energy `=qDeltaV` `=1.6xx10^(-19)xx1` `[ because DeltaV =1V]` `=1.6xx10^(-19)`j This unit of energy is defined as 1 electron voltor 1 eV. Definition:"if an electron according through a potential difference of ONE volt the difference in potential (or kinetic) energy of an electron is known as one electron volt". This unit are most commonly used in atomic , nuclear and particle physics. Multiplier and submultiplier of eV: `I meV 1.6 xx 10^(-22) J ` `1 KEV = 1.6 xx 10^(-16)`j `1 Me = 1.6xx10^(-13) J` `1 GE V = 1.6xx10^(-10) J` `1 TEV= 1.6xx10^(-7) `J |
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| 10. |
In a samemedium and at a same temperature , velocities of two sound waves of frequencies 200Hz and 400Hz will be = a ratio : |
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Answer» 1:2 |
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| 11. |
Two small spheres are attached to the ends of a long light nonconducting rod at a distance 40 mm from each other. All three spheres are nonconducting, have identical masses m = 1 g, and a positive charge q = 1C is distributed evenly on the surface of each sphere. The whole system is placed on a horizontal frictionless nonconducting surface. Initially, all three spheres are at rest and the middle sphere is located a distance 30 mm from one of the ends of the rod and a distance 10 mm from the other. Find the maximum speed v (in ms^(-1))of the middle sphere after the system is released. |
Answer» Solution : SINCE the charge is evely distributed, the charges can be treated as point charges. Looking at the "believe" and "after" pictures and taking right as positive and left as negative, CONSERVATION of momentum gives `sumvecP_(b)=sumvecP_(a)` `0=2mv_(2)-mv_(1)`,which gives `v_(2)=V_(1)//2` The maximum velocity of the middle charge will occur when the middle charge is at the middle. Beyond the middle point, there will be a net force to the right that will tend to slow the charge down. The situation will be the same for the middle charge even if the two end charges are moving. Applying the LAW of conservation of energy to the SYSTEM and using the middle charge position of maximum velocity as the "after" position, one gets `E_(b)=E_(a)` `PE_(b)=KE+PE_(a)` or `(kq^(2))/(3d)+(kq^(2))/(d)=(1)/(2)mv_(1)^(2)+(1)/(2)(2m)v_(2)^(2)+(2kq^(2))/(2d)` Now using the conservation of momentum RESULT above for `v_(2)` and simplifying, we get or `(kq^(2))/(3d)=(1)/(2)mv_(1)^(2)+m(v_(1)^(2))/(4)=(3mv_(1)^(2))/(4)` Finally solving for the maximum velocity `v_(1)=(2q)/(3) sqrt((k)/(md))=20 ms^(-1)` |
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| 12. |
Two different sound sources s_(1) and s_(2) have frequencies ratio 1:2. Source s, is approaching towards an observer and s_(2) is receding from the same observer. Speeds of both s_(1) and s_(2) are the same and equal to v. speed of sound in air in 300 m/s. If no beats are heard by the observer the value of V is 1 |
| Answer» Answer :B | |
| 13. |
Control rods used in nuclear reactors are made of |
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Answer» STEEL |
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| 14. |
An insulated container containing n moles of monoatomic gas of molar mass m is moving with a velocity v_0. If the container is suddenly stopped, find the change in temperature. |
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Answer» `(mnv_0^2)/(3R)` molar mass of the gas = m, Total mass of the gas in the container, M=mn Change in KE of the gas when the container is suddenly STOPPED, i.e, `DeltaK=(KE)_"INITIAL"-(KE)_"final"=1/2Mv_0^2-0=1/2Mv_0^2 = 1/2 mnv_0^2` This change in kinetic energy (`DeltaK`) RESULT in a change in internal energy (`DeltaU`) of the gas. `DeltaU=nC_VDeltaT=n(3/2R)DeltaT` Here, `DeltaT` is the change in temperature of the gas. As `DeltaU=DeltaK, n(3/2 R)DeltaT=1/2mnv_0^2 therefore DeltaT=(mnv_0^2)/(3R)` |
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| 15. |
Describe briefly three experimentally observed features in the phenomenon of photoelectric effect. |
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Answer» Solution :Experimentally observed features in the phonomenon of photoelectric effect are as follows: (i) For a given metal and frequency of incident radiation (above the THRESHOLD frequency), the number of photoelectrons emitted per second is DIRECTLY proportional to the INTENSITY of incident light. (ii) For a given metal, there exists a certain minimum frequency (threshold frequency) of incident radiation, below which no emission of photoelectrons takes PLACE. (iii) Above the threshold frequency, the maximum kinetic energy of emitted photoelectrons is directly proportional to the frequency of incident radiation but is independent of the intensity of the intensity of incident radiation. Moreover, photoelectric emission is an instantaneous process without anytime `lag(~10^(-9)s` or even less), even when the incident radiation is very DIM. |
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| 16. |
Statement I: Stopping potential depends upon the frequency of incident light but is independent of the intensity of the light. Statement II: The maximum kinetic energy of the photoelectrons is proportional to stopping potential. |
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Answer» A. STATEMENT-I is false, statement-II is TRUE. |
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| 17. |
Assertion (A) : A capacitor blocks d.c. but offers an easy path to a.c. Reason (R) : Capacitive reactance is inversely proportional to frequency of a.c. supply. |
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Answer» If both ASSERTION and reason are true and the reason is the CORRECT explanation of the assertion. |
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| 18. |
Match the following : {:(,"Column -I",,"Column -II"),((A),"Acceleration due to gravity",(p),"Kepler's law"),((B),"Law of periods",(q),"Vector quantity"),((C ),"Orbital speed",(r ),"Uniform near earth surface"),((D),"Gravitational potential",(s),"Is nearly zero at infinity"):} |
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| 19. |
A wire of length 40 cm which has a mass of 4 gms oscillates in its second harmonic and sets the air column in the tube to vibrations in its fundamental mode as shown in figure. Assuming speed of sound in air as 340 m/s, find the tension in the wire. |
| Answer» Answer :A | |
| 20. |
Current flowing in the direction of -ve charge is called _______ |
| Answer» SOLUTION :ELECTRIC CURRENT | |
| 21. |
A potential difference across 24Omega resistor is 12 V. What is the current through the resistor? |
Answer» SOLUTION : `V=12V` and `R=24Omega` CURRENT, `I=?` From Ohm.s law, `I=(V)/(R )=(12)/(24)=0.5A` |
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| 22. |
A potentiometer wire , 4 m long and having a resistance of 10 Omega, is connected in series with an external resistance of 38 Omega and a cell , ofemf 2 V and internal resistance 2 Omega. Calculate thepotential gradient along the wire. |
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Answer» Solution :Date : ` L = 4 m , R = 10 Omega, E = 2 V, r_(C) = 2 Omega, R = 39 Omega` The POTENTIAL difference across the wire is `V = Ir = (E/(r + r_(c) + R))r` ` :. ` The potential gradient along the wire is ` V/L = (Er)/((r + r_(c )+R)L) ` ` =(2 xx 10)/((10 + 2 + 38) xx4) ` ` = (20)/(50 xx 4) = 20/200 = 0.1` V/m |
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| 23. |
If a transmission line in a cold climate collects ice, the increased diameter tends to cause vortex formation in a passing wind. The air pressure variations in the vortexes lend to cause the line to oscillate (gallop), especially if the frequency of the variations matches a resonant frequency of the line. In long lines, the resonant frequencies are so close that almost any wind speed can set up a resonant mode vigorous enough to pull down support towers or cause the line to short on with an adjacent line. If transmission line has a length of 310 m, id linear density of 3.35 kg/mı, and a tension of 90.1 MN, what are the frequency of the fundamentail made and (b) the frequency difference between sucessive modes? |
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| 24. |
Current flowing in the direction of +ve charge is called _______ |
| Answer» SOLUTION :CONVENTIONAL CURRENT | |
| 25. |
The magnetic flux of 500mu Wbper turn passing through a 200 turn coil is reversed in 20 xx 10^(-3)seconds. The average e.m.f. induced in the coil in volt is |
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Answer» 2.5 |
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| 26. |
An object falling through a fluid is observed to have acceleration given by a =g -bv where g=gravitational acceleration and b is constant.After a long time of release,it is observed to fall with constant speed.The value of constant speed is |
| Answer» Answer :A | |
| 27. |
This question contains statement-I and statement-II of the four choice given after the statement, choose the one that best describes the two statements. Statement I : The temperature dependence of resistance is usually given as R = R_(0) (1 +alpha Deltat). The resistance of a wire changes from 100 Omega" to " 150 Omega when its temperature is increased from 27^(@)C" to "227^(@)C. This impilies that alpha = 25xx 10^(-3)""^(@)C. Statement II: R = R_(0) (1+ alphaDelta t)) is valid only when the change in the temperature Delta T is small and Delta R= (R- R_(0)) lt lt R_(0). |
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Answer» STATEMENT-I is true, statement-II is true, LTBGT statement-II is not the correct explanation of statement-I. |
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| 28. |
A 22cm long tube containing 88cc of sugar produces an optical rotation of 9.9^(@) when placed in a polarimeter. If the amount of sugar in the solution is 6g, calculation the specific rotation. |
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| 29. |
The masses are connected with a spring & a string as shown they are initially at rest with springs at its natural length & string too at its original length fing the maximum extension in the spring after the forces start acting as shown |
| Answer» Solution :`f(x_(1)+x_(2))=1/2k(m_(1)+m_(2))^(2) (2f)/k-(m_(1)+m_(2))` | |
| 30. |
In a two slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by a distance of 5 xx 10^(-2) m towards the slits, the change in the fringe width is 3 xx 10^(-5) m. If the separation be. tween the slits is 10^(-3) m, the wavelength of light used is : |
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Answer» `5 XX 10^(-7)` m |
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| 31. |
When a sphere rolls without slipping the ratio of its kinetic energy of translation to its total kinetic energy is |
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Answer» 1:7 |
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| 32. |
What do you mean by drift velocity? |
| Answer» SOLUTION :The AVERAGE velocity acquired by an ELECTRON under the applied electric field is called drift velocity. | |
| 33. |
Two point charges 2 muC and 0.1 muC are held at a separation of 20 mm. What work is required by the external agent to move the charges to half of the given separation? |
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Answer» Solution :Here, Work done = Final potential energy - Initial potential energy `rArr W=(1)/(4pi epsilon_(0)) (q_(1)q_(2))/(r.)-(1)/(4pi epsilon_(0)) (q_(1)q_(2))/(r )` Here, `q_(1)=2muC= 2XX10^(-6)C` `q_(2)=0.1muC=0.1 XX 10^(-6)C` `r.=` Final separation between `q_(1) and q_(2)` `=10 m m=10xx10^(-3)m` r = Initial separation between `q_(1) and q_(2)` `=20 mm=20xx10^(-3)m` `therefore W=(q_(1)q_(2))/(4pi epsilon_(0)) [(1)/(r.)-(1)/(r )]` `=9xx10^(9)xx2xx10^(-6)xx0.1xx10^(-6)` `[(1)/(10xx10^(-3))-(1)/(20xx10^(-3))]` `=9xx10^(9)xx2xx10^(-6)xx0.1xx10^(-6)xx(1,000)/(20)` `=9xx10^(-2)J` |
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| 34. |
Obtain the expression for the energy stored in a capacitor connected across a dc battery. Hence define energy density of the capacitor. |
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Answer» Solution :Let at a particular instant CHARGE on the plate of capacitor be q and its potential difference be `(q)/(C )` . If an ADDITIONAL charge dg is GIVEN to the capacitor plate, work done for it is given by `dW = (q)/(C ).qq` Therefore, whole process of charging from 0 to Q requires a work `W= int_(0)^(Q)(qdq)/(C )=(1)/(C) [(q^(2))/(2)]_(0)^(Q)=(Q^(2))/(2C)` This work done is stored as the electrostatic potential energy U of the charged capacitor. MOREOVER, Q=CV, where V be the potential difference between the plates of capacitor, HENCE `U= (Q^(2))/(2C)= (1)/(2)QV=(1)/(2)CV^(2)` Energy per unit volume of the capacitor is called its energy density u. It can be easily shown that u `=(1)/(2)in_(0)E^(2)` where E = electric field between the plates of capacitor. |
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| 35. |
(i) Draw a neat labelled ray diagram of a compound microscope . Explain briefly its working . (ii) Why must both the objective and the eye-piece of a compound microscope have short focal lengths ? |
| Answer» SOLUTION :(ii) Both the objectives `f_(0)` and PIECE `f_(E)` have short focal lengths for large magnifying POWER. | |
| 36. |
For destructive interference to take place between two monochromatic light waves of wavelength lambda, the path difference should be |
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Answer» `((2N-1)LAMBDA)/(4)` |
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| 37. |
A conducting circular loop is placed in a uniform magnetic field of 0.04 T with its plane perpendicular to the field. Some how, the radius of the loop starts shrinking at a constant rate of 2 mm/s. Find the induced emf in the loop at an instant when the radius becomes 2 cm solution. |
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Answer» Solution :Let the RADIUS of the loop be r at time t the magnetic flux linked with the loop at this instant is, `phi=AB=pir^2B` The induced emf in the loop at time t, `|epsilon|=(dphi)/(dt)` `=d/(dt)[pir^2B]` `=2pirB(DR)/(dt)` Here B=0.04 T , r=2 cm `=2xx10^(-2)` m `(dr)/(dt)=2 (mm)/s` `=2xx10^(-3)m/s` `=2pixx2xx10^(-2)xx0.04xx2xx10^(-3)` `therefore |epsilon|=0.32pixx10^(-5)V` `therefore |epsilon|=3.2pixx10^(-6)V=3.2pi MUV` |
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| 38. |
Shift on the principal axis |
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Answer» GREATER than the FOCAL length of EYE piece |
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| 39. |
Assertion If a charged particle enters from outside in uniform magnetic field, then it will keep on rotating in a circular path. Reson Magnetic force is always perpendicular to velocity vector. |
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Answer» If both Assertion and Reason are TRUE and Reason is the CORRECT explanationof Assertion. |
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| 40. |
A parallelplate capacitor is made of two circular plates separatedby a distanc of 5mm and with a dielectric of dielectric constant 2.2 between them . When the electric field in the dielectric is 3xx10^(4)V/m the charge density of the positive platewill be close to : |
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Answer» `3xx10^(4) C//m^(2)` `E = (sigma)/(K in_(0))` `:. Sigma = KE in_(0) = 2.2 xx3xx10^(4) xx8.85 xx10^(-12)` `= 58.41xx10^(-8) = 6 xx10^(-7) C //m^(2)` |
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| 41. |
The highest frequency of transmitted wave that is returned to the earth by layer of ionosphere after having been sent straight (normally) to it, is called |
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Answer» MAXIMUM USABLE frequency |
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| 42. |
The ratio of the resolving power of an electron microscope to that of an ordinary microscope is |
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Answer» 400 times |
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| 43. |
Twelve infinite ling wire of unifrom linear charge density (lambda) are passing along the twelve edges of a cube. Find electric flux through any face of cube. |
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Answer» `((lambdal)/(2epsilon_(0)))` |
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| 44. |
Arrange radioactive radiation in the increasing order of penetrating power. |
| Answer» SOLUTION :`ALPHA,BETA GAMMA` | |
| 45. |
Ray incidents at 60^(@) and reflected ray gets completely polarized, then speed of refracted light in denser medium is ...... |
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Answer» <P>`SQRT(2)` `(C)/(v)= sqrt(3)` `:. v=(c)/(sqrt(3))=(3xx10^(8))/(sqrt(3))=sqrt(3)xx10^(8) ms^(-1)` |
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| 46. |
A parallel-plate capacitor is clamped to a stand such that its plates are vertical. It remains connected to a cell through a centre-zero galvanometer. A metal sheet which is parallel to the plate of the capacitor and whose thickness is slightly less than the seperation between these plates is now allowed to fall under gravity though the plates, wihtout touching them. Which of the following correctly describes the deflection(s) of the galvanometer? |
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Answer» It will SHOW a constant deflection to ONE side only, as long as the sheet is PASSING through the plates. |
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| 47. |
A prism can produce a minmum deviation delta in a the beam. If three such prisms are combined, the minimum deviation that can be produced in this beam is |
| Answer» Answer :B | |
| 48. |
The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true ? |
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Answer» Its KINETIC energy INCREASES and its potential and TOTAL energies decrease. |
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| 49. |
The magnetic splitting spectral lines called Zeeman effect was confirmed by |
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Answer» Newton.s CORPUSCULAR theory |
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| 50. |
The count rate of a radioactive sample falls from 4.0xx10^6 s^(-1) to 1.0xx10^6 s^(-1) in 20 hours. What will be the count rate after 100 hours from beginning ? |
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Answer» `3.91xx10^3 s^(-1)` t=20 hours, t'=100 hours As,`R/R_0(1/2)^n` or `(1.0xx10^6)/(4.0xx10^6)=(1/2)^n` or `(1/2)^n = (1/2)^2 THEREFORE n=2` `T_(1//2)=t/n=20/2`=10 hours Now, `n'="t'"/T_(1//2)=100/10`=10 `therefore R'=R_0(1/2)^(n') =4.0xx10^6 (1/2)^10 = 3.91xx10^3 s^(-1)` |
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