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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 41151. |
The poet took the road... |
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Answer» To the right |
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| 41152. |
Statement - I : A body which is good radiator is is good absorber of radiation at a given wavelength. Statement - II : According to Kirchhoff's law, the absorptivity of a body is equal to its emissivity at a given wavelength. |
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Answer» Statement - I is TRUE, Statement - II is true and Statement - I is correct explanation for Statement - II. So correct CHOICE is (a). |
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| 41153. |
The ratio of the radius of the tube of a venturimeter is eta (eta gt 1) . The ratio of the densities of the liquid in the manometer and the moving fluidis eta _(1) . If the differencein heights of the liquid column in the manometer is h , find the minimum speed of flow of the fluid . |
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Answer» Solution :The speed of FLOW is minimum whenthe cross - sectional AREA of the tube is maximum . The equation foe minimumspeed of FLOWOF the liquidin a venturimeter is GIVEN as `v_(1) = A_(2) sqrt((2rho_(0)gh)/(rho(A_(1)^(2)-A_(2)^(2))))= sqrt((2(rho_(0)//rho)gh)/(((A_(1))/(A_(2)))^(2)-1))` Putting `rho_(0)//rho = eta_(1) , (A_(1))/(A_(2))= (pir_(1)^(2))/(pir_(2)^(2)) = (r_(1)/(r_(2)))^(2) = ETA^(2)` , we obtain , `v_(1) = sqrt((2eta_(1)gh)/(eta^(4)-1))` |
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| 41154. |
The frequency of visible light is of the order of: |
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Answer» `10^(15)` Hz |
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| 41155. |
An object viewed directly through a rectangular slan 12 cm thick appears to be raised by 4 cm. The refractive index of the material of slab is ________. |
| Answer» Solution :Hint : Refractive index `N=("real THICKNESS")/("APPARENT thickness")=(12CM)/((12-4)cm)=1.5` | |
| 41156. |
The time taken by sunlight to cross a 5 mm thick glass plate (mu=3//2) is |
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Answer» `0.25xx10^(-10)` s |
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| 41157. |
The battery of an automobile is connected to a starting motor by straight wires 70 cm long and 1.5 cm apart. If, at the time of starting, the current in the wire is 300 A, estimate the force between the wires . Is the force attractive or repulsive? |
| Answer» SOLUTION :0.84 N,REPULSIVE | |
| 41158. |
Calculate the value of the resistance of R in the circuit shown in the so that the current in the circuit is 0.2A .What would be the potential difference between points B and E ? (##CHY_DMB_PHY_XII_P1_U02_C02_E23_001_Q01.png" width="80%"> |
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Answer» Let R = equivalent resistance between B and E . Then,`(1)/(r)=(1)/(30)+(1)/(10)+(1)/(15)=(1+3+2)/(30)=(6)/(30)=(1)/(5)` i . e ,`r=5Omega` `THEREFORE` The potential differnce between points B and E `Ir=0.2xx5=1V` Effective emf of the CIRCUIT= 8- 3 = 5 V `therefore0.2=(5)/(15+R+5)=(5)/(20+R)` `"or," 4+0.2R=5` ` "or," R=(5-4)/(0.2)=5Omega` |
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| 41159. |
A coil of area 150cm^2having 250 turns carriers a current of 2 mA. It is suspended in a uniform magnetic field of induction 9 xx 10^(-3) "Wbm"^(-2). Its plane makes an angle of 60^0 with the line of induction. Find the torque acting on the coil. |
| Answer» SOLUTION :`3.375 XX 10^(-5) NM` | |
| 41160. |
A cylinder (m=10 kg) is rolling in a plane with an initial velocity of 10 m/s . If coefficient of friction between the surface and the cylinder is 1/2 , then before stopping , it will describe the distance |
| Answer» Answer :A | |
| 41161. |
A loop of wire is turned round the vertical axis by 180° in a uniform magnetic field so that at the beginning of motion the point A moves toward the observer while the point C moves away from the observer. The direction of current, induced in the loop, is |
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Answer» PERMANENTLY from A to C |
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| 41162. |
If N_P and N_S are respectively no. of turns in primary and secondary coil then for step up transformer, |
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Answer» `N_S gt N_P` For STEP up TRANSFORMER `epsilon_S gt epsilon_P RARR N_S gt N_P` |
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| 41163. |
A boy throws a ball in air in such a manner that when the ball is in its max. height, he throws another ball. If the balls are thrown after the time difference of 1 s, then what will be the height attained by them: |
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Answer» 19.6 m |
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| 41164. |
Arrangement of four wall layers in microsporangium from inside to outside in follows |
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Answer» EPIDERMIS,ENDOTHECIUM TAPETUM and MIDDLE LAYERS |
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| 41165. |
Find the equivalent resistance of the network in fig. between points A and C. |
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Answer» Solution :The resistance `R_1 ` is CONNECTED in series with RESISTOR of `7.5 Omega`, hence the EQUIVALENT resistance between POINTS A and C is, `R_2 = (R_1 + 7.5) ` ohm = `(7.5+7.5)` ohm = `15 Omega` |
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| 41167. |
A particle with a mass of 0.2 kg moves according to the law s=0.08cos(20pit+(pi)/(4)) Find the velocity of the particle, its acceleration and the acting force, as well as the amplitudes of the respective quantities. |
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Answer» SOLUTION :We have `1+cos^(2)t+sin^(4)t=1+(1)/(2)(1+cos2t)+(1)/(4)(1-cos2t)^(2)=(1)/(4)(4+2+2cos2t+1-2tcos^(4)2t` `=(1)/(4)[7+(1)/(2)(1+cos4t)]=(1)/(8)(15+cos4t)` Henec it follows `s=(1)/(8)+(15+cos4t)sin500t=` `=(15)/(8)sin500t+(1)/(8)sin500t.cos4t=` `=(15)/(8)sin500t+(1)/(16)sin504t+(1)/(16)sin496t` The spectrum is SHOW in Fig 
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| 41168. |
Magnetic lines of force due to a bar magnet do not intersect because |
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Answer» A point always has a single NET magnetic field |
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| 41169. |
Consider the following R-L-C circuit in which R = 12 Omega, X_(L) =24Omega, X_(C) =8Omega The emf of source is given by V =10 sin (100pit)V (a) Find the energey dissipated in 10 min (b) If resistance is removed from the circuit and value of inductance is doubled express variation of current with time t in the new circuit . . |
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Answer» Solution :Inpedance `Z = sqrt(R^(2) + (X_(L) - X_(C)^(2))) = sqrt((12)^(2) + (24 - 8)^(2)) = 20Omega` `cops phi = ( R)/(Z) = (12)/(20) = (3)/(5)` Power consumed ` P = (1)/(2) V_(0)i_(0) cos phi = (1)/(2) V_(0) . V_(0)/(Z) cos phi` ` = (1)/(2) (10)^(2)/((20)) xx (3)/(5) = 1.5W` Energy dissipated `E = Pt = (1.5)(10 xx 60) =900J` `Z = X_(L) - X_(C) = 48 -8 =40 Omega` `i_(0) = (V_(0))/(Z) = (10)/(40) = (1)/(4) A` Current lags the voltage by `pi//2` `i = i_(0) SIN (omegat -pi//2)` `= (1)/(4) sin (100 pit - 2)`   .
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| 41170. |
What we call the instrument which converts sound waves into electrical waves? |
| Answer» SOLUTION :MICROPHONE | |
| 41171. |
Pick the odd one out of the following based on electricfield intensity. |
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Answer» POINT charge |
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| 41172. |
a) Determine the 'eefective focal length' of the combination of the two lenses in Exercise 10, if they are placed 8.0 cm apart with their principal axes coincident. Does the answer depend on which side of the combination a beam of parallel light is incident ? Is the notion of effective focal length of this system useful at all ? |
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Answer» Solution :i) Let a parallel beam be incident on the convex LENS first. If 2nd lens were absent, then `u_(1)=oo and f_(1)=30cm` As `(1)/(upsilon_(1))-(1)/(u_(1))=(1)/(f_(1))` `(1)/(upsilon_(1))=(1)/(oo)=(1)/(30)` `upsilon_(1)=30cm` The image would now act as a virtual object for 2nd lens. `u_(2)=+(30-8)=+22cm` `upsilon_(2)=?, f_(2)=-20cm` As `(1)/(upsilon_(2))=(1)/(f_(2))+(1)/(u_(2))` `(1)/(upsilon_(2))=(1)/(-20)+(1)/(22)=(-11+10)/(220)=(-1)/(220)` `upsilon_(2)=-220cm` `therefore` Parallel incident beam would appear to diverge from a point `220-4=216cm` from the centre of the two lens system. ii) Suppose a parallel beam of light fromthe LEFT is incident first on the concave lens. `u_(1)=-oo, f_(1)=-20cm, upsilon=?` As `(1)/(upsilon_(1))-(1)/(u_(1))=(1)/(f_(1))` `(1)/(upsilon_(1))=(1)/(f_(1))+(1)/(u_(1))=(-1)/(20)+(1)/(-oo)=(-1)/(20)` This image acts as a real object for the 2nd lens. `u_(2)=-(20+8)=-28cm, f_(2)=30cm,` `upsilon_(2)=?` As `(1)/(upsilon_(2))-(1)/(u_(2))=(1)/(f_(2))` `(1)/(upsilon_(2))=(1)/(f_(2))+(1)/(u_(2))=(1)/(30)-(1)/(28)=(14-15)/(420)` `upsilon_(2)=-420 CM` `therefore` The parallel beam appears to diverge from a point `420-4=416cm`, on the left of the centre of the two lens system. From the above discussion, we observe that the anwer depends on which side of the lens system the parallel beam is incident. Therefore, the notion of effective focal length does not SEEM to be useful here. |
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| 41173. |
In the following question a statement of assertion (A) is followed by a statement of reason (R ) A: If E be electric field at a point , in free space then energy density at that point will be (1)/(2) epsilon_(0)E^(2) . R , electrostatic field is a conservative field . |
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Answer» If both Assertion & Reason are TRUE and the reason is the correct explanation of the assertion , then MARK (1). |
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| 41174. |
(a) Magnetic field lines show the direction (at every point) along which a small magnetised needle aligns at the point). Do the magnetic field lines also represent the lines of force on a moving charged particle at every point? (b) Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why? (c) If magnetic monopoles existed, how would the Gauss's law of magnetism be modified? (d) Does a bar magnet exert a torque on itsell due to its own field? Does one element of a current-carrying wire exert a force on another element of the same wtre? (e) Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero? |
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Answer» Solution :(a) No. The MAGNETIC force is always normal to B (remember magnette force `=qv xx B).` It is misleading to call magiette fteld ithes as lines of force. (b) If field lines were ENTIRELY confined between two ends of a straight solenoid, the flux through the cross-section at each end would be non-zero. But the flux of field B through any closed surface must always be zero. For a toroid, this difficulty is absent because it has no .ends.. (c) Gauss.s law of magnetism states that the flux of B through any closed surface is always zero `int_(s) B. triangleS=0` If monopoles EXISTED, the right hand side would be equal to the monopole (magnetic charge) `q_(m)` enclosed by S. (Analogous to Gauss.s law of electrostaties, `int_(S) B. triangleS=mu_(0)q_(m)" where "q_(m)` is the (monopole) magnetic charge enclosed by S.) (d) No. There is no force or torque on an element due to the field produced by that element itself. But there is a force (or torque) on an element of the same wire. (For the special case of a straight wire, this force is zero.) (E) Yes. THe average of the charge in the system may be zer. Yet, the mean of the magnetic moments due to various current loops may not be zero. We will come across such examples in connection with paramagnetic material where atoms have net dipole moment thorugh their net charge is zero. |
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| 41175. |
A convex lens of focal length 15 cm is split into two halves and the two halves are placed at a separation of 120 cm. Between the two halves of convex lens a plane mir- ror is placed horizontally and at a distance of 4 mm below the principal axis of the lens halves. An object AB of length 2 mm is placed at a distance of 20 cm from one half lens as shown in figure. Find the distance of final image of the point A from the principal axis. |
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Answer» |
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| 41176. |
One toroid has 1.5 xx 10^4 turns and its axis forms a circle of radius 10 cm. Its cross-section has radius 2 cm. Find inductance of this toroidal ring. |
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Answer» |
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| 41177. |
In Wheatstone's network P = 2 Omega , Q = 2 Omega , R = 2 Omegaand S = 3 OmegaThe resistance with which S is to shunted in order that the bridge may be balanced is |
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Answer» `6Omega` `(2)/(2) = (2)/((3 xx x)/(3 + x)) rArr (3X)/(3+ x)=2 rArr 3x = 6+ 2x rArr x= 6 Omega` |
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| 41178. |
Which of the statements given in Exerciseis true for p-type semiconductos. |
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Answer» ELECTRONS are majority CARRIERS and trivalent atoms are the dopants. |
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| 41179. |
Select the correct option: |
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Answer» With increase in INTENSITY of INCIDENT light, photoelectric current DECREASES. |
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| 41180. |
A moving coil galvanometer has a current sensitivity of 10div/mA and voltage sensitivity of 5div/volt. The instrument has 50 divisions. Calculate the resistance of the galvanometer. DATA: No. of divisions=50 Current sensitivity = 10 div/mA therefore Maximum current = 50/10 5mA = 5xx10^(-3) A Voltage sensitivity = 5 div/volt therefore Maximum P.D = 50/5=10V To find: resistance=? |
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Answer» Solution :RESISTANCE(GALVANOMETER) `=(P.D.)/(max. current)=(10)/(5XX10^(-3))=2000Omega` |
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| 41181. |
In the circuit shown in the figure all the resistances are identical and each has the value r Omega. The equivalent resistance of the combination between the points A and B will remain unchanged even when the following pairs of points marked in the figure are connected through a resistance R. |
Answer» Solution :Theequivalentresistanceof thecombinationbetweenthe pointsA andB willremains unchangedevenafter conncecting resistance` R,`whencircuitfollowsa conditionof balancedwheatstonebridge ` therefore` for thecircuitto remainatbalancedcondition `(2 r)/( 4 r)implies ( P)/(Q )= (M)/(N)` so newresistanceR canconectedbetweenpointsmarked2 AND6  Againfor thecircuitto remainat balancedcondition`(4r)/(2 r)=( 2r)/( r ) implies(P )/( Q ) =(M )/(N)` So newresistance can beconnectedbetweenpointsmarked4 and 7 . |
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| 41182. |
Force exist on a current carrying wire which is placed in external magnetic field, due to :– |
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Answer» free ELECTRONS in wire |
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| 41183. |
An alternating e.m.f. is applied to a series L-C-R circuit. If the frequency of the applied e.m.f is more then the resonant frequency of the circuit then the circuit will act as : |
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Answer» a RESISTIVE circuit |
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| 41184. |
The melting point of copper is 1,080^(@)C and its heat of fusion is 200kJ/kg. if a copper coin at this temperature is completely melted by the absorption of 2,000 J of heat, what is the mass of the coin? |
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Answer» `(1)/(1,080kg)` `m=(Q)/(L)=(2000J)/(200kJ//kg)=(2000J)/(200xx10^(3)J//kg)=(1)/(100)kg`. |
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| 41185. |
On passing current through a solenoid. Which of its end behave as a north pole or south pole explain ? |
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Answer» Solution :When current flows from LOOP (coil) it behave as magnet. Its one face behave as N pole while opposite face will behave as S pole. Which end of coil behave as N pole and which end behave as a S pole can be found by following method. (1) When closed current loop is viewed NORMALLY and if the current SEEMS to flow in clockwise DIRECTION then that side of the loop BEHAVES as a south pole and the other side of the loop behaves as a north pole It is shown in figure.  (2) Similarly, if the current seems to flow in anticlockwise direction then the side of the loop towards eye behaves as a north pole and the other side as a south pole. |
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| 41186. |
A: If a spring block system, oscillating in a vertical plane is made to oscillate on a horizontal surface, the time period will remain same. R: The time period of spring block system does not depend on g. |
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Answer» If both ASSERTION & Reason are true and the reason is the correct EXPLANATION of the assertion, then mark (1) |
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| 41187. |
Figure shows to concentric conducting spherical shells, each initialy carrying a charge Q. The amount of heat generated in the system when the two shells are joined by a conducting wire by closing the switch S is ((Q//n)^(2))/(piepsilon_(0)a) where n is an integer. Calculate the value of n |
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Answer» `=(Q^(2))/(2XX(4piepsilon_(0))/(1/a-1/(2A)))=(Q^(2))/(16piepsilon_(0)a)` 
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| 41188. |
A hollow conducting sphere of inner radius r and outer radius 2R is given charge Q as shown in figure, then the |
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Answer» POTENTIAL at A and B is same. points `A` and `B` LIE within the same metal HENCE `V_(A)=V_(B)`. The potential inside a HOLLOW sphere is same as potential at the surface, hence `V_(A)=V_(B)=V_(C)=V_(0)`. |
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| 41189. |
LASER light is considered to be coherent because it consists of |
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Answer» MANY wavelengths |
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| 41190. |
On hot summer days while removing in a bus the distant spot on highway appears to be wet even though it is not actually wet which physical phenomenon is responsible for this effect ? |
| Answer» SOLUTION :TOTAL INTERNAL REFLECTION | |
| 41191. |
On hot summer days while removing in a bus the distant spot on highway appears to be wet even though it is not actually wet. How snell's law is modified in this situation ? |
| Answer» SOLUTION :`n=1/sin C` | |
| 41192. |
Answer the following questions: (c) A diver under water, looks obliquely at a fisherman standing on the bank of a lake. Would the fisherman look taller or shorter to the diver than what he actually is? |
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Answer» SOLUTION :Taller. `rArr` Let pure water is filled in a vessel. A fish is there at the bottom as an observer. `rArr` Fish observes the eye of a man by keeping its vision in direction of OQ. As shown in figure, by extending OQ in air it will meet at E. on normal of surface.  `rArr` HENCE, fish observes eye of man at El instead of E. `rArr` Here, EP `= h_0` which is real height of eye from surface and `E.P =h_i` which is apparent height of eye from surface. `rArr` From this we can conclude that if object is in RARER medium and observer is in denser medium, then IMAGE will be appeared to be shifted up `h_1 gt h_0`. |
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| 41193. |
Although the surface of a goggle lens are curved yet it does not have any power. |
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Answer» |
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| 41194. |
A certain prism is found to produce a minimum deviation of 38° It produces a deviation of 44^@ when the angle of incidence is either 42^@ or 62^@. What is the angle of incidence when it is undergoing minimum deviation? |
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Answer» `49^@` `d= 42^@ +62^@-A ` `44^@= 104 -A ` `A=60^@` `D-m= 2i-A ` ` 98^@= 2 I - 60^@` ` 98^@ = 2i implies I = 49^@` |
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| 41195. |
The maximum intensity in Young's double slit experiment is I_0. Distance between the slits is d = 5lamda , where lamdais the wavelength of monochromatic light used in the experiment. What will be the intensity of light in front of one of the slits on a screen at a distance D=10d ? |
| Answer» SOLUTION :`(I_0)/(2)` | |
| 41196. |
The greatest length of a steel wire that can be hung vertically without breaking (breaking stress for steel = 7.9 xx 10^(8) N/m, density of steel wire = 7.9 xx 10^(3) kg//m^(3)) |
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Answer» `9xx10^(9)m` `=(7.9xx10^(8))/(7.9xx10^(3)xx10))=10^(4)m` So the correct choice is (B). |
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| 41197. |
In a Young's double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit distance D must be changed to, |
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Answer» 2D Same FRINGE SPACE,`beta=beta.implies(lambdaD)/(d)=(lambdaD.)/(2d),D.=2D` |
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| 41198. |
How is a photodiode Fabricated ? |
| Answer» Solution : PHOTO diode is FABRICATED with a TRANSPARENT window to ALLOW light to fall on the diode. | |
| 41200. |
The breaking tension of a string is 80 kg wt. A mass of 1 kg is attached to the string and rotated in a horizontal surface of radius 2 m. What is the maximum revolution made without breaking |
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Answer» 3.2 rps |
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