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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 8151. |
A stone is hung in air from a wire which is stretched over a sonometer. The bridges of the sonometer are L cm apart when the wire is in unison with a tuning fork of frequency N. When the stone is completely immersed in water, the length between the bridges is l cm for re-establishing unison, the specific gravity of the material of the stone is |
| A. | \[\frac{{{L}^{2}}}{{{L}^{2}}+{{l}^{2}}}\] |
| B. | \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] |
| C. | \[\frac{{{L}^{2}}}{{{L}^{2}}-{{l}^{2}}}\] |
| D. | \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] |
| Answer» D. \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] | |
| 8152. |
A uniform rod of length 2.0 m is suspended through an end and is set into oscillation with small amplitude under gravity. The time period of oscillation is approximately [AMU (Med.) 2000] |
| A. | 1.60 sec |
| B. | 1.80 sec |
| C. | 2.0 sec |
| D. | 2.40 sec |
| Answer» E. | |
| 8153. |
In the following circuit, bulb rated as 1.5 V, 0.45 W. If bulbs glows with full intensity then what will be the equivalent resistance between X and Y |
| A. | 0.45 W |
| B. | 1 W |
| C. | 3 W |
| D. | 5 W |
| Answer» C. 3 W | |
| 8154. |
A parallel plate air capacitor has a capacitance of \[100\mu \mu F\]. The plates are at a distance \[d\]apart. If a slab of thickness \[t(t\le d)\]and dielectric constant 5 is introduced between the parallel plates, then the capacitance will be [MP PMT 2003] |
| A. | \[50\mu \mu F\] |
| B. | \[100\mu \mu F\] |
| C. | \[200\mu \mu F\] |
| D. | \[500\mu \mu F\] |
| Answer» D. \[500\mu \mu F\] | |
| 8155. |
A concave mirror is placed on a horizontal table with its axis directed vertically upwards. Let \[O\]be the pole of the mirror and\[C\] its centre of curvature. A point object is placed at \[C.\] It has a real image, also located at \[C.\] If the mirror is now filled with water, the image will be [IIT-JEE 1998] |
| A. | Real, and will remain at C |
| B. | Real, and located at a point between C and \[\infty \] |
| C. | Virtual and located at a point between C and O |
| D. | Real, and located at a point between C and O |
| Answer» E. | |
| 8156. |
A point object is moving on the principal axis of a concave mirror of focal length \[24cm\] towards the mirror. When it is at a distance of \[60cm\] from the mirror, its velocity is \[9cm/sec.\] What is the velocity of the image at that instant [MP PMT 1997] |
| A. | \[5cm/sec\] towards the mirror |
| B. | \[4cm/sec\] towards the mirror |
| C. | \[4cm/sec\] away from the mirror |
| D. | \[9cm/\sec \] away from the mirror |
| Answer» D. \[9cm/\sec \] away from the mirror | |
| 8157. |
A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be |
| A. | 1 mA |
| B. | 2 mA |
| C. | 4 mA |
| D. | None of these |
| Answer» D. None of these | |
| 8158. |
A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is [IIT 1995; UPSEAT 2002] |
| A. | 1080 |
| B. | 2430 |
| C. | 3240 |
| D. | 4860 |
| Answer» B. 2430 | |
| 8159. |
How much length of a very thin wire is required to obtain a solenoid of length \[{{l}_{0}}\] and inductance L |
| A. | \[\sqrt{\frac{2\pi L{{l}_{0}}}{{{\mu }_{0}}}}\] |
| B. | \[\sqrt{\frac{4\pi L{{l}_{0}}}{\mu _{0}^{2}}}\] |
| C. | \[\sqrt{\frac{4\pi L{{l}_{0}}}{{{\mu }_{0}}}}\] |
| D. | \[\sqrt{\frac{8\pi L{{l}_{0}}}{{{\mu }_{0}}}}\] |
| Answer» D. \[\sqrt{\frac{8\pi L{{l}_{0}}}{{{\mu }_{0}}}}\] | |
| 8160. |
In a Ag voltameter 2.68 gm of silver is deposited in 10 min. The heat developed in \[20\,\Omega \] resistor during the same period will be |
| A. | 192 kJ |
| B. | 192 J |
| C. | 200 J |
| D. | 132 kJ |
| Answer» B. 192 J | |
| 8161. |
Which of the following function represents a simple harmonic oscillation [AIIMS 2005] |
| A. | \[\sin \omega t-\cos \omega t\] |
| B. | \[{{\sin }^{2}}\omega t\] |
| C. | \[\sin \omega x+\sin 2\omega t\] |
| D. | \[\sin \omega x-\sin 2\omega t\] |
| Answer» B. \[{{\sin }^{2}}\omega t\] | |
| 8162. |
In the following circuit a 10 m long potentiometer wire with resistance 1.2 ohm/m, a resistance R1 and an accumulator of emf 2 V are connected in series. When the emf of thermocouple is 2.4 mV then the deflection in galvanometer is zero. The current supplied by the accumulator will be |
| A. | 4 ´ 10?4 A |
| B. | 8 ´ 10?4 A |
| C. | 4 ´ 10?3 A |
| D. | 8 ´ 10?3 A |
| Answer» B. 8 ´ 10?4 A | |
| 8163. |
Four charges equal to ? Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium the value of q is [AIEEE 2004] |
| A. | \[-\frac{Q}{4}(1+2\sqrt{2})\] |
| B. | \[\frac{Q}{4}(1+2\sqrt{2})\] |
| C. | \[-\frac{Q}{2}(1+2\sqrt{2})\] |
| D. | \[\frac{Q}{2}(1+2\sqrt{2})\] |
| Answer» C. \[-\frac{Q}{2}(1+2\sqrt{2})\] | |
| 8164. |
An alternating voltage of 141.4V (rms) is applied to a vacuum diode as shown in the figure. The maximum potential difference across the condenser will be |
| A. | 100 V |
| B. | 200 V |
| C. | \[100\sqrt{2}V\] |
| D. | \[200\sqrt{2}V\] |
| Answer» C. \[100\sqrt{2}V\] | |
| 8165. |
The half life of radium is 1620 years and its atomic weight is 226 kgm per kilomol. The number of atoms that will decay from its 1 gm sample per second will be [MP PMT 1993; BVP 2003] |
| A. | \[3.61\times {{10}^{10}}\] |
| B. | \[3.6\times {{10}^{12}}\] |
| C. | \[3.11\times {{10}^{15}}\] |
| D. | \[31.1\times {{10}^{15}}\] (Avogadro's number \[N=6.02\times {{10}^{26}}\]atom/kilomol) |
| Answer» B. \[3.6\times {{10}^{12}}\] | |
| 8166. |
A 12 V lead accumulator is being charged using 24 V supply with an external resistance \[2\,\Omega \]. The internal resistance of the accumulator is\[1\,\Omega \]. Find the time in which it will store 360 W-hour energy. |
| A. | 1 hr |
| B. | 7.5 hr |
| C. | 10 hr |
| D. | None of these |
| Answer» C. 10 hr | |
| 8167. |
A string of length L and mass M hangs freely from a fixed point. Then the velocity of transverse waves along the string at a distance x from the free end is |
| A. | \[\sqrt{gL}\] |
| B. | \[\sqrt{gx}\] |
| C. | \[gL\] |
| D. | \[gx\] |
| Answer» C. \[gL\] | |
| 8168. |
The amplitude of a damped oscillator becomes half in one minute. The amplitude after 3 minute will be \[\frac{1}{X}\]times the original, where X is [CPMT 1989; DPMT 2002] |
| A. | \[2\times 3\] |
| B. | \[{{2}^{3}}\] |
| C. | \[{{3}^{2}}\] |
| D. | \[3\times {{2}^{2}}\] |
| Answer» C. \[{{3}^{2}}\] | |
| 8169. |
As the switch S is closed in the circuit shown in figure, current passed through it is |
| A. | 4.5 A |
| B. | 6.0 A |
| C. | 3.0 A |
| D. | Zero |
| Answer» B. 6.0 A | |
| 8170. |
A charged particle q is shot towards another charged particle Q which is fixed, with a speed \[\nu \]. It approaches Q upto a closest distance r and then returns. If q were given a speed \[2\nu \], the closest distances of approach would be [AIEEE 2004] |
| A. | r |
| B. | 2r |
| C. | r/2 |
| D. | r/4 |
| Answer» E. | |
| 8171. |
The extension in a string obeying Hooke's law is x. The speed of sound in the stretched string is v. If the extension in the string is increased to 1.5x, the speed of sound will be [IIT 1996] |
| A. | 1.22 v |
| B. | 0.61 v |
| C. | 1.50 v |
| D. | 0.75 v |
| Answer» B. 0.61 v | |
| 8172. |
A mass M is split into two parts, m and (M?m), which are then separated by a certain distance. What ratio of m/M maximizes the gravitational force between the two parts [AMU 2000] |
| A. | 1/3 |
| B. | 1/2 |
| C. | 1/4 |
| D. | 1/5 |
| Answer» C. 1/4 | |
| 8173. |
A particle of mass m is moving in a horizontal circle of radius r under a centripetal force equal to \[-K/{{r}^{2}}\], where K is a constant. The total energy of the particle is [IIT 1977] |
| A. | \[\frac{K}{2r}\] |
| B. | \[-\frac{K}{2r}\] |
| C. | \[-\frac{K}{r}\] |
| D. | \[\frac{K}{r}\] |
| Answer» C. \[-\frac{K}{r}\] | |
| 8174. |
With the usual notations, the following equation \[{{S}_{t}}=u+\frac{1}{2}a(2t-1)\] is |
| A. | Only numerically correct |
| B. | Only dimensionally correct |
| C. | Both numerically and dimensionally correct |
| D. | Neither numerically nor dimensionally correct |
| Answer» D. Neither numerically nor dimensionally correct | |
| 8175. |
A short linear object of length \[l\] lies along the axis of a concave mirror of focal length f at a distance \[u\] from the pole of the mirror. The size of the image is approximately equal to [IIT-JEE 1988; BHU 2003; CPMT 2004] |
| A. | \[l{{\left( \frac{u-f}{f} \right)}^{1/2}}\] |
| B. | \[l{{\left( \frac{u-f}{f} \right)}^{2}}\] |
| C. | \[l{{\left( \frac{f}{u-f} \right)}^{1/2}}\] |
| D. | \[l{{\left( \frac{f}{u-f} \right)}^{2}}\] |
| Answer» E. | |
| 8176. |
In PN-junction diode the reverse saturation current is \[{{10}^{-5}}\]amp at\[27{}^\circ C.\] The forward current for a voltage of \[0.2volt\] is [MP PMT 1993] |
| A. | \[2037.6\times {{10}^{-3}}amp\] |
| B. | \[203.76\times {{10}^{-3}}amp\] |
| C. | \[20.376\times {{10}^{-3}}amp\] |
| D. | \[2.0376\times {{10}^{3}}amp\] \[[\exp (7.62)=2038.6,\,K=1.4\times {{10}^{-23}}J/K]\] |
| Answer» D. \[2.0376\times {{10}^{3}}amp\] \[[\exp (7.62)=2038.6,\,K=1.4\times {{10}^{-23}}J/K]\] | |
| 8177. |
A sodium atom is in one of the states labeled 'Lowest excited levels'. It remains in that state for an average time of 10?8 sec, before it makes a transition back to a ground state. What is the uncertainty in energy of that excited state |
| A. | 6.56 ´ 10?8 eV |
| B. | 2 ´ 10?8 eV |
| C. | 10?8 eV |
| D. | 8 ´ 10?8 eV |
| Answer» B. 2 ´ 10?8 eV | |
| 8178. |
When photon of energy 4.25 eV strike the surface of a metal A, the ejected photoelectrons have maximum kinetic energy TA eV and de-Brolie wavelength \[{{\lambda }_{A}}\]. The maximum kinetic energy of photoelectrons liberated from another metal B by photon of energy 4.70 eV is \[{{T}_{B}}=({{T}_{A}}-1.50)\ eV\]. If the de-Broglie wavelength of these photoelectrons is \[{{\lambda }_{B}}=2{{\lambda }_{A}}\], then [IIT-JEE 1994] |
| A. | The work function of A is 2.25 eV |
| B. | The work function of B is 4.20 eV |
| C. | \[{{T}_{A}}=2.00\ eV\] |
| D. | \[{{T}_{B}}=2.75\ eV\] |
| Answer» C. \[{{T}_{A}}=2.00\ eV\] | |
| 8179. |
In the circuit given below, what will be the reading of the voltmeter [RPET 1996] |
| A. | 300 V |
| B. | 900 V |
| C. | 200 V |
| D. | 400 V |
| Answer» D. 400 V | |
| 8180. |
An e.m.f. of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time \[t=\infty \] and at t = 1 second is [MP PMT 1994] |
| A. | \[\frac{{{e}^{1/2}}}{{{e}^{1/2}}-1}\] |
| B. | \[\frac{{{e}^{2}}}{{{e}^{2}}-1}\] |
| C. | \[1-{{e}^{-1}}\] |
| D. | \[{{e}^{-1}}\] |
| Answer» C. \[1-{{e}^{-1}}\] | |
| 8181. |
If a magnet is suspended at an angle 30o to the magnetic meridian, it makes an angle of 45o with the horizontal. The real dip is |
| A. | \[{{\tan }^{-1}}(\sqrt{3}/2)\] |
| B. | \[{{\tan }^{-1}}(\sqrt{3)}\] |
| C. | \[{{\tan }^{-1}}(\sqrt{3/2})\] |
| D. | \[{{\tan }^{-1}}(2/\sqrt{3})\] |
| Answer» B. \[{{\tan }^{-1}}(\sqrt{3)}\] | |
| 8182. |
Two straight long conductors AOB and COD are perpendicular to each other and carry currents \[{{i}_{1}}\] and \[{{i}_{2}}\]. The magnitude of the magnetic induction at a point P at a distance a from the point O in a direction perpendicular to the plane ACBD is [MP PMT 1994] |
| A. | \[\frac{{{\mu }_{0}}}{2\pi a}({{i}_{1}}+{{i}_{2}})\] |
| B. | \[\frac{{{\mu }_{0}}}{2\pi a}({{i}_{1}}-{{i}_{2}})\] |
| C. | \[\frac{{{\mu }_{0}}}{2\pi a}{{(I_{1}^{2}+I_{2}^{2})}^{1/2}}\] |
| D. | \[\frac{{{\mu }_{0}}}{2\pi a}\frac{{{I}_{1}}{{I}_{2}}}{({{I}_{1}}+{{I}_{2}})}\] |
| Answer» D. \[\frac{{{\mu }_{0}}}{2\pi a}\frac{{{I}_{1}}{{I}_{2}}}{({{I}_{1}}+{{I}_{2}})}\] | |
| 8183. |
A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is |
| A. | 44 |
| B. | 20 |
| C. | 22 |
| D. | 33 |
| Answer» E. | |
| 8184. |
A train has just complicated a U-curve in a track which is a semicircle. The engine is at the forward end of the semicircular part of the track while the last carriage is at the rear end of the semicircular track. The driver blows a whistle of frequency 200 Hz. Velocity of sound is 340 m/sec. Then the apparent frequency as observed by a passenger in the middle of a train when the speed of the train is 30 m/sec is |
| A. | 209 Hz |
| B. | 288 Hz |
| C. | 200 Hz |
| D. | 181 Hz |
| Answer» D. 181 Hz | |
| 8185. |
Two blocks A and B each of mass m are connected by a massless spring of natural length L and spring constant K. The blocks are initially resting on a smooth horizontal floor with the spring at its natural length as shown in figure. A third identical block C also of mass m moves on the floor with a speed v along the line joining A and B and collides with A. Then [IIT-JEE 1993] |
| A. | The kinetic energy of the A-B system at maximum compression of the spring is zero |
| B. | The kinetic energy of the A-B system at maximum compression of the spring is \[m{{v}^{2}}/4\] |
| C. | The maximum compression of the spring is \[v\sqrt{m/K}\] |
| D. | The maximum compression of the spring is \[v\sqrt{m/2K}\] |
| Answer» C. The maximum compression of the spring is \[v\sqrt{m/K}\] | |
| 8186. |
A cylinder of radius R made of a material of thermal conductivity \[{{K}_{1}}\] is surrounded by a cylindrical shell of inner radius R and outer radius 2R made of material of thermal conductivity\[{{K}_{2}}\]. The two ends of the combined system are maintained at two different temperatures. There is no loss of heat across the cylindrical surface and the system is in steady state. The effective thermal conductivity of the system is [IIT 1988; MP PMT 1994, 97; SCRA 1998] |
| A. | \[{{K}_{1}}+{{K}_{2}}\] |
| B. | \[\frac{{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}}\] |
| C. | \[\frac{{{K}_{1}}+3{{K}_{2}}}{4}\] |
| D. | \[\frac{3{{K}_{1}}+{{K}_{2}}}{4}\] |
| Answer» D. \[\frac{3{{K}_{1}}+{{K}_{2}}}{4}\] | |
| 8187. |
Two identical containers A and B with frictionless pistons contain the same ideal gas at the same temperature and the same volume V. The mass of the gas in A is \[{{m}_{A}}\] and that in B is \[{{m}_{B}}\]. The gas in each cylinder is now allowed to expand isothermally to the same final volume 2V. The changes in the pressure in A and B are found to be \[\Delta P\] and 1.5 \[\Delta P\] respectively. Then [IIT 1998] |
| A. | \[4{{m}_{A}}=9{{m}_{B}}\] |
| B. | \[2{{m}_{A}}=3{{m}_{B}}\] |
| C. | \[3{{m}_{A}}=2{{m}_{B}}\] |
| D. | \[9{{m}_{A}}=3{{m}_{B}}\] |
| Answer» D. \[9{{m}_{A}}=3{{m}_{B}}\] | |
| 8188. |
An iron tyre is to be fitted on to a wooden wheel 1m in diameter. The diameter of tyre is 6 mm smaller than that of wheel. The tyre should be heated so that its temperature increases by a minimum of (the coefficient of cubical expansion of iron is 3.6 × 10?5/ºC) [CPMT 1989] |
| A. | 167ºC |
| B. | 334ºC |
| C. | 500ºC |
| D. | 1000ºC |
| Answer» D. 1000ºC | |
| 8189. |
The sum of the magnitudes of two forces acting at point is 18 and the magnitude of their resultant is 12. If the resultant is at 90° with the force of smaller magnitude, what are the, magnitudes of forces [Roorkee 1992; AIEEE 2002] |
| A. | 12, 5 |
| B. | 14, 4 |
| C. | 5, 13 |
| D. | 10, 8 |
| Answer» D. 10, 8 | |
| 8190. |
A solid metallic sphere has a charge \[+\,3Q\]. Concentric with this sphere is a conducting spherical shell having charge \[-Q\]. The radius of the sphere is \[a\] and that of the spherical shell is \[b(b>a)\]. What is the electric field at a distance \[R(a |
| A. | \[\frac{Q}{2\pi {{\varepsilon }_{0}}R}\] |
| B. | \[\frac{3Q}{2\pi {{\varepsilon }_{0}}R}\] |
| C. | \[\frac{3Q}{4\pi {{\varepsilon }_{0}}{{R}^{2}}}\] |
| D. | \[\frac{4Q}{4\pi {{\varepsilon }_{0}}{{R}^{2}}}\] |
| Answer» D. \[\frac{4Q}{4\pi {{\varepsilon }_{0}}{{R}^{2}}}\] | |
| 8191. |
In a surface tension experiment with a capillary tube water rises upto 0.1 m. If the same experiment is repeated on an artificial satellite, which is revolving around the earth, water will rise in the capillary tube upto a height of [Roorkee 1992] |
| A. | 0.1 m |
| B. | 0.2 m |
| C. | 0.98 m |
| D. | Full length of the capillary tube |
| Answer» E. | |
| 8192. |
A container is filled with water (m = 1.33) upto a height of 33.25 cm. A concave mirror is placed 15 cm above the water level and the image of an object placed at the bottom is formed 25 cm below the water level. The focal length of the mirror is [IIT-JEE (Screening) 2005] |
| A. | 10 |
| B. | 15 |
| C. | 20 |
| D. | 25 |
| Answer» D. 25 | |
| 8193. |
The relation between Ip and Vp for a triode is \[{{I}_{p}}=(0.125{{V}_{p}}-7.5)\,mA\]Keeping the grid potential constant at 1V, the value of rp will be |
| A. | 8 kW |
| B. | 4 kW |
| C. | 2 kW |
| D. | 8 kW |
| Answer» E. | |
| 8194. |
A photon collides with a stationary hydrogen atom in ground state inelastically. Energy of the colliding photon is 10.2 eV. After a time interval of the order of micro second another photon collides with same hydrogen atom inelastically with an energy of 15 eV. What will be observed by the detector [IIT-JEE (Screening) 2005] |
| A. | 2 photon of energy 10.2 eV |
| B. | 2 photon of energy of 1.4 eV |
| C. | One photon of energy 10.2 eV and an electron of energy 1.4 eV |
| D. | One photon of energy 10.2 eV and another photon of 1.4 eV |
| Answer» D. One photon of energy 10.2 eV and another photon of 1.4 eV | |
| 8195. |
A wire cd of length l and mass m is sliding without friction on conducting rails ax and by as shown. The vertical rails are connected to each other with a resistance R between a and b. A uniform magnetic field B is applied perpendicular to the plane abcd such that cd moves with a constant velocity of |
| A. | \[\frac{mgR}{Bl}\] |
| B. | \[\frac{mgR}{{{B}^{2}}{{l}^{2}}}\] |
| C. | \[\frac{mgR}{{{B}^{3}}{{l}^{3}}}\] |
| D. | \[\frac{mgR}{{{B}^{2}}l}\] |
| Answer» C. \[\frac{mgR}{{{B}^{3}}{{l}^{3}}}\] | |
| 8196. |
The wiring of a house has resistance \[6\,\Omega .\] A 100 W bulb is glowing. If a geyser of 1000 W is switched on, the change in potential drop across the bulb is nearly [MNR 1998] |
| A. | Nil |
| B. | 23 V |
| C. | 32 V |
| D. | 12 V |
| Answer» C. 32 V | |
| 8197. |
A person speaking normally produces a sound intensity of 40 dB at a distance of 1 m. If the threshold intensity for reasonable audibility is 20 dB, the maximum distance at which he can be heard clearly is |
| A. | 4 m |
| B. | 5 m |
| C. | 10 m |
| D. | 20 m |
| Answer» D. 20 m | |
| 8198. |
Two simple pendulums whose lengths are 100 cm and 121 cm are suspended side by side. Their bobs are pulled together and then released. After how many minimum oscillations of the longer pendulum, will the two be in phase again [DPMT 2005] |
| A. | 11 |
| B. | 10 |
| C. | 21 |
| D. | 20 |
| Answer» C. 21 | |
| 8199. |
Potential difference across the terminals of the battery shown in figure is (r = internal resistance of battery) |
| A. | 8 V |
| B. | 10 V |
| C. | 6 V |
| D. | Zero |
| Answer» E. | |
| 8200. |
A light source is located at \[{{P}_{1}}\] as shown in the figure. All sides of the polygon are equal. The intensity of illumination at \[{{P}_{2}}\] is \[{{I}_{0}}\]. What will be the intensity of illumination at \[{{P}_{3}}\] |
| A. | \[\frac{3\sqrt{3}}{8}{{I}_{0}}\] |
| B. | \[\frac{{{I}_{0}}}{8}\] |
| C. | \[\frac{3}{8}{{I}_{0}}\] |
| D. | \[\frac{\sqrt{3}}{8}{{I}_{0}}\] |
| Answer» B. \[\frac{{{I}_{0}}}{8}\] | |