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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.
| 8501. |
A black metal foil is warmed by radiation from a small sphere at temperature T and at a distance \[d\]. It is found that the power received by the foil is `P'. If both the temperature and the distance are doubled, the power received by the foil will be [MP PMT 1997] |
| A. | 16P |
| B. | 4P |
| C. | 2P |
| D. | P |
| Answer» C. 2P | |
| 8502. |
When an ideal monoatomic gas is heated at constant pressure, fraction of heat energy supplied which increases the internal energy of gas, is [AIIMS 1995] |
| A. | \[\frac{2}{5}\] |
| B. | \[\frac{3}{5}\] |
| C. | \[\frac{3}{7}\] |
| D. | \[\frac{3}{4}\] |
| Answer» C. \[\frac{3}{7}\] | |
| 8503. |
A lead bullet at 27°C just melts when stopped by an obstacle. Assuming that 25% of heat is absorbed by the obstacle, then the velocity of the bullet at the time of striking (M.P. of lead = 327°C, specific heat of lead = 0.03 cal/gm°C, latent heat of fusion of lead = 6 cal/gm and J = 4.2 joule/cal) [IIT 1981] |
| A. | 410 m/sec |
| B. | 1230 m/sec |
| C. | 307.5 m/sec |
| D. | None of the above |
| Answer» B. 1230 m/sec | |
| 8504. |
In the circuit shown below E1 = 4.0 V, R1= 2 W, E2 = 6.0 V, R2 = 4 W and R3 = 2 W. The current I1 is [MP PET 2003] |
| A. | 1.6 A |
| B. | 1.8 A |
| C. | 1.25 A |
| D. | 1.0 A |
| Answer» C. 1.25 A | |
| 8505. |
A satellite is launched into a circular orbit of radius R around the earth. A second satellite is launched into an orbit of radius (1.01)R. The period of the second satellite is larger than that of the first one by approximately [IIT 1995] |
| A. | 0.5% |
| B. | 1.0% |
| C. | 1.5% |
| D. | 3.0% |
| Answer» D. 3.0% | |
| 8506. |
Two particles of masses \[{{m}_{1}}\] and \[{{m}_{2}}\] in projectile motion have velocities \[{{\vec{v}}_{1}}\] and \[{{\vec{v}}_{2}}\] respectively at time t = 0. They collide at time \[{{t}_{0}}\]. Their velocities become \[{{\vec{v}}_{1}}'\] and \[{{\vec{v}}_{2}}'\] at time \[2{{t}_{0}}\] while still moving in air. The value of \[|({{m}_{1}}\overrightarrow{{{v}_{1}}}'\,+{{m}_{2}}\overrightarrow{{{v}_{2}}}')-({{m}_{1}}\overrightarrow{{{v}_{1}}}\,+{{m}_{2}}\overrightarrow{{{v}_{2}}})\]| is [IIT-JEE Screening 2001] |
| A. | Zero |
| B. | \[({{m}_{1}}+{{m}_{2}})g{{t}_{0}}\] |
| C. | \[2({{m}_{1}}+{{m}_{2}})g{{t}_{0}}\] |
| D. | \[\frac{1}{2}({{m}_{1}}+{{m}_{2}})g{{t}_{0}}\] |
| Answer» D. \[\frac{1}{2}({{m}_{1}}+{{m}_{2}})g{{t}_{0}}\] | |
| 8507. |
The coordinates of a particle moving in a plane are given by \[=-\ 8\ m/{{s}^{2}}.\] and \[y(t)=b\sin (pt)\] where \[a,\,\,b\,( |
| A. | The path of the particle is an ellipse |
| B. | The velocity and acceleration of the particle are normal to each other at \[t=\pi /(2p)\] |
| C. | The acceleration of the particle is always directed towards a focus |
| D. | The distance travelled by the particle in time interval \[t=0\] to \[t=\pi /(2p)\] is \[a\] |
| Answer» B. The velocity and acceleration of the particle are normal to each other at \[t=\pi /(2p)\] | |
| 8508. |
The periodic time of rotation of a certain star is 22 days and its radius is 7 ' 108 metres. If the wavelength of light emitted by its surface be\[4320\,\,{AA}\], the Doppler shift will be (1 day = 86400 sec) [MP PET 2001] |
| A. | \[0.033\,\,{AA}\] |
| B. | \[0.33\,\,{AA}\] |
| C. | \[3.3\,\,{AA}\] |
| D. | \[33\,\,{AA}\] |
| Answer» B. \[0.33\,\,{AA}\] | |
| 8509. |
In the circuit given below, V(t) is the sinusoidal voltage source, voltage drop VAB(t) across the resistance R is [IIT 1993] |
| A. | Is half wave rectified |
| B. | Is full wave rectified |
| C. | Has the same peak value in the positive and negative half cycles |
| D. | Has different peak values during positive and negative half cycle |
| Answer» E. | |
| 8510. |
A neutron with velocity V strikes a stationary deuterium atom, its kinetic energy changes by a factor of [DCE 2000] |
| A. | \[\frac{15}{16}\] |
| B. | \[\frac{1}{2}\] |
| C. | \[\frac{2}{1}\] |
| D. | None of these |
| Answer» E. | |
| 8511. |
The reading of ammeter in the circuit shown will be |
| A. | 2A |
| B. | 2.4 A |
| C. | Zero |
| D. | 1.7 A |
| Answer» D. 1.7 A | |
| 8512. |
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be [IIT JEE (Screening) 2001] |
| A. | Maximum in situation |
| B. | Maximum in situation |
| C. | Maximum in situation |
| D. | The same in all situations |
| Answer» B. Maximum in situation | |
| 8513. |
If \[{{\varphi }_{1}}\] and \[{{\varphi }_{2}}\] be the angles of dip observed in two vertical planes at right angles to each other and f be the true angle of dip, then |
| A. | \[{{\cos }^{2}}\varphi ={{\cos }^{2}}{{\varphi }_{1}}+{{\cos }^{2}}{{\varphi }_{2}}\] |
| B. | \[{{\sec }^{2}}\varphi ={{\sec }^{2}}{{\varphi }_{1}}+{{\sec }^{2}}{{\varphi }_{2}}\] |
| C. | \[{{\tan }^{2}}\varphi ={{\tan }^{2}}{{\varphi }_{1}}+{{\tan }^{2}}{{\varphi }_{2}}\] |
| D. | \[{{\cot }^{2}}\varphi ={{\cot }^{2}}{{\varphi }_{1}}+{{\cot }^{2}}{{\varphi }_{2}}\] |
| Answer» E. | |
| 8514. |
For a positively charged particle moving in a x-y plane initially along the x-axis, there is a sudden change in its path due to the presence of electric and/or magnetic fields beyond P. The curved path is shown in the x-y plane and is found to be non-circular. Which one of the following combinations is possible [IIT-JEE (Screening) 2003] |
| A. | \[\overrightarrow{E}=0;\,\overrightarrow{B}=b\hat{i}\,+c\hat{k}\] |
| B. | \[\overrightarrow{E}=ai;\,\overrightarrow{B}=c\hat{k}\,+a\hat{i}\] |
| C. | \[\overrightarrow{E}=0;\,\overrightarrow{B}=c\hat{j}\,+b\hat{k}\] |
| D. | \[\overrightarrow{E}=ai;\,\overrightarrow{B}=c\hat{k}\,+b\hat{j}\] |
| Answer» C. \[\overrightarrow{E}=0;\,\overrightarrow{B}=c\hat{j}\,+b\hat{k}\] | |
| 8515. |
A silver voltameter of resistance 2 ohm and a 3 ohm resistor are connected in series across a cell. If a resistance of 2 ohm is connected in parallel with the voltameter, then the rate of deposition of silver [EAMCET 1983] |
| A. | Decreases by 25% |
| B. | Increases by 25% |
| C. | Increases by 37.5% |
| D. | Decreases by 37.5% |
| Answer» E. | |
| 8516. |
An observer moves towards a stationary source of sound with a speed 1/5th of the speed of sound. The wavelength and frequency of the source emitted are \[\lambda \] and \[f\] respectively. The apparent frequency and wavelength recorded by the observer are respectively [CBSE PMT 2003] |
| A. | \[1.2\ f,\ \lambda \] |
| B. | \[f,\ 1.2\lambda \] |
| C. | \[0.8f,\ 0.8\lambda \] |
| D. | \[1.2f,\ 1.2\lambda \] |
| Answer» B. \[f,\ 1.2\lambda \] | |
| 8517. |
The bob of a simple pendulum is displaced from its equilibrium position O to a position Q which is at height h above O and the bob is then released. Assuming the mass of the bob to be m and time period of oscillations to be 2.0 sec, the tension in the string when the bob passes through O is [AMU 1995] |
| A. | \[m\,(g+\pi \sqrt{2g\,h})\] |
| B. | \[m\,(g+\sqrt{{{\pi }^{2}}g\,h})\] |
| C. | \[m\,\left( g+\sqrt{\frac{{{\pi }^{2}}}{2}g\,h} \right)\] |
| D. | \[m\,\left( g+\sqrt{\frac{{{\pi }^{2}}}{3}g\,h} \right)\] |
| Answer» B. \[m\,(g+\sqrt{{{\pi }^{2}}g\,h})\] | |
| 8518. |
A black body is at a temperature of \[2880\ K\]. The energy of radiation emitted by this object with wavelength between \[499\ nm\] and \[500\ nm\] is \[{{U}_{1}}\], between \[999\ nm\] and \[1000\ nm\] is \[{{U}_{2}}\] and between \[1499\ nm\] and \[1500\ nm\] is \[{{U}_{3}}\]. The Wein's constant\[b=2.88\times {{10}^{6}}\ nm\,K\]. Then [IIT 1998] |
| A. | \[{{U}_{1}}=0\] |
| B. | \[{{U}_{3}}=0\] |
| C. | \[{{U}_{1}}>{{U}_{2}}\] |
| D. | \[{{U}_{2}}>{{U}_{1}}\] |
| Answer» E. | |
| 8519. |
Water of volume 2 litre in a container is heated with a coil of \[1\,kW\] at \[27\,{}^\circ C\]. The lid of the container is open and energy dissipates at rate of \[160\,J/s.\] In how much time temperature will rise from \[27\,{}^\circ C\] to \[77\,{}^\circ C\] [Given specific heat of water is \[4.2\,kJ/kg\]] [IIT-JEE (Screening) 2004] |
| A. | 8 min 20 s |
| B. | 6 min 2 s |
| C. | 7 min |
| D. | 14 min |
| Answer» B. 6 min 2 s | |
| 8520. |
In the circuit shown here, E1 = E2 = E3 = 2 V and R1 = R2 = 4 ohms. The current flowing between points A and B through battery E2 is [MP PET 2001] |
| A. | Zero |
| B. | 2 amp from A to B |
| C. | 2 amp from B to A |
| D. | None of the above |
| Answer» C. 2 amp from B to A | |
| 8521. |
The charge on \[500\,cc\] of water due to protons will be [RPET 1997] |
| A. | \[6.0\times {{10}^{27}}C\] |
| B. | \[2.67\times {{10}^{7}}C\] |
| C. | \[6\times {{10}^{23}}C\] |
| D. | \[1.67\times {{10}^{23}}C\] |
| Answer» C. \[6\times {{10}^{23}}C\] | |
| 8522. |
A projectile is projected with velocity \[k{{v}_{e}}\] in vertically upward direction from the ground into the space. (\[{{v}_{e}}\] is escape velocity and \[k |
| A. | \[\frac{R}{{{k}^{2}}+1}\] |
| B. | \[\frac{R}{{{k}^{2}}-1}\] |
| C. | \[\frac{R}{1-{{k}^{2}}}\] |
| D. | \[\frac{R}{k+1}\] |
| Answer» D. \[\frac{R}{k+1}\] | |
| 8523. |
A vessel at rest explodes into three pieces. Two pieces having equal masses fly off perpendicular to one another with the same velocity 30 meter per second. The third piece has three times mass of each of other piece. The magnitude and direction of the velocity of the third piece will be [AMU (Engg.) 1999] |
| A. | \[10\sqrt{2}\,m/second\] and \[135{}^\circ \] from either |
| B. | \[10\sqrt{2}\,m/second\] and \[45{}^\circ \] from either |
| C. | \[\frac{10}{\sqrt{2}}\,m/second\] and \[135{}^\circ \] from either |
| D. | \[\frac{10}{\sqrt{2}}\,m/second\] and \[45{}^\circ \] from either |
| Answer» B. \[10\sqrt{2}\,m/second\] and \[45{}^\circ \] from either | |
| 8524. |
If 97.52 is divided by 2.54, the correct result in terms of significant figures is |
| A. | 38.4 |
| B. | 38.3937 |
| C. | 38.394 |
| D. | 38.39 |
| Answer» B. 38.3937 | |
| 8525. |
A rocket is going towards moon with a speed v. The astronaut in the rocket sends signals of frequency \[\nu \] towards the moon and receives them back on reflection from the moon. What will be the frequency of the signal received by the astronaut (Take v |
| A. | \[\frac{c}{c-v}\nu \] |
| B. | \[\frac{c}{c-2v}\nu \] |
| C. | \[\frac{2v}{c}\nu \] |
| D. | \[\frac{2c}{v}\nu \] |
| Answer» C. \[\frac{2v}{c}\nu \] | |
| 8526. |
The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If VB = 5 V, then the maximum value of R so that the voltage is above the knee point, will be |
| A. | 4.3 kW |
| B. | 860 kW |
| C. | 4.3 W |
| D. | 860 W |
| Answer» B. 860 kW | |
| 8527. |
The ionisation potential of H-atom is \[13.6\,V\]. When it is excited from ground state by monochromatic radiations of \[970.6\,{AA}\], the number of emission lines will be (according to Bohr?s theory) [RPET 1999] |
| A. | 10 |
| B. | 8 |
| C. | 6 |
| D. | 4 |
| Answer» D. 4 | |
| 8528. |
X-rays of wavelength 0.1 Å allowed to fall on a metal get scattered. The wavelength of scattered radiation is 0.111 Å. If h = 6.624 \[\times \]10?34 J-s and m0 = 9 \[\times \]10?31 kg, then the direction of the scattered photons will be |
| A. | cos?1 (0.547) |
| B. | cos?1 (0.4484) |
| C. | cos?1 (0.5) |
| D. | cos?1 (0.3) |
| Answer» B. cos?1 (0.4484) | |
| 8529. |
Match the following Currents r.m.s. values (1) \[{{x}_{0}}\sin \omega \,t\] (i) x0 (2) \[{{x}_{0}}\sin \omega \,t\cos \omega \,t\] (ii) \[\frac{{{x}_{0}}}{\sqrt{2}}\] (3) \[{{x}_{0}}\sin \omega \,t+{{x}_{0}}\cos \omega \,t\] (iii) \[\frac{{{x}_{0}}}{(2\sqrt{2})}\] |
| A. | 1. (i), 2. (ii), 3. (iii) |
| B. | 1. (ii), 2. (iii), 3. (i) |
| C. | 1. (i), 2. (iii), 3. (ii) |
| D. | None of these |
| Answer» C. 1. (i), 2. (iii), 3. (ii) | |
| 8530. |
A coil of wire having finite inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t = 0, so that a time-dependent current \[{{I}_{1}}(t)\] starts flowing through the coil. If \[{{I}_{2}}(t)\] is the current induced in the ring. and \[B(t)\] is the magnetic field at the axis of the coil due to \[{{I}_{1}}(t),\] then as a function of time (t > 0), the product I2 (t) B(t) [IIT-JEE (Screening) 2000] |
| A. | Increases with time |
| B. | Decreases with time |
| C. | Does not vary with time |
| D. | Passes through a maximum |
| Answer» E. | |
| 8531. |
Two identical bar magnets with a length 10 cm and weight 50 gm-weight are arranged freely with their like poles facing in a inverted vertical glass tube. The upper magnet hangs in the air above the lower one so that the distance between the nearest pole of the magnet is 3mm. Pole strength of the poles of each magnet will be |
| A. | 6.64 amp ´ m |
| B. | 2 amp ´ m |
| C. | 10.25 amp ´ m |
| D. | None of these |
| Answer» B. 2 amp ´ m | |
| 8532. |
A particle of mass m and charge q moves with a constant velocity v along the positive x direction. It enters a region containing a uniform magnetic field B directed along the negative z direction, extending from x = a to x = b. The minimum value of v required so that the particle can just enter the region \[x>b\] is [IIT-JEE (Screening) 2002] |
| A. | \[qb\,B/m\] |
| B. | \[q(b-a)B/m\] |
| C. | \[qa\,B/m\] |
| D. | \[q(b+a)B/2m\] |
| Answer» C. \[qa\,B/m\] | |
| 8533. |
Silver and copper voltameter are connected in parallel with a battery of e.m.f. 12 V. In 30 minutes, 1 gm of silver and 1.8 gm of copper are liberated. The power supplied by the battery is [IIT 1975] |
| A. | 24.13 J/sec |
| B. | 2.413 J/sec |
| C. | 0.2413 J/sec |
| D. | 2413 J/sec \[({{Z}_{Cu}}=6.6\times {{10}^{-4}}gm/C\] and \[{{Z}_{Ag}}=11.2\times {{10}^{-4}}\,gm/C)\] |
| Answer» B. 2.413 J/sec | |
| 8534. |
A police car moving at 22 m/s, chases a motorcyclist. The police man sounds his horn at 176 Hz, while both of them move towards a stationary siren of frequency 165 Hz. Calculate the speed of the motorcycle, if it is given that he does not observes any beats [IIT-JEE (Screening) 2003] |
| A. | 33 m/s |
| B. | 22 m/s |
| C. | Zero |
| D. | 11 m/s |
| Answer» C. Zero | |
| 8535. |
Two simple pendulums of length 5 m and 20 m respectively are given small linear displacement in one direction at the same time. They will again be in the phase when the pendulum of shorter length has completed .... oscillations. [CBSE PMT 1998; JIPMER 2001, 02] |
| A. | 5 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» D. 3 | |
| 8536. |
Two bodies \[A\]and \[B\] have thermal emissivities of 0.01 and 0.81 respectively. The outer surface areas of the two bodies are the same. The two bodies emit total radiant power at the same rate. The wavelength \[{{\lambda }_{B}}\] corresponding to maximum spectral radiancy in the radiation from \[B\] is shifted from the wavelength corresponding to maximum spectral radiancy in the radiation from \[A\], by \[1.00\mu m\]. If the temperature of \[A\] is \[5802\ K\] [IIT 1994; DCE 1996] |
| A. | The temperature of \[B\] is \[1934\ K\] |
| B. | \[{{\lambda }_{B}}=1.5\mu m\] |
| C. | The temperature of \[B\] is \[11604\ K\] |
| D. | The temperature of \[B\] is \[2901\ K\] |
| Answer» B. \[{{\lambda }_{B}}=1.5\mu m\] | |
| 8537. |
The temperature of a hypothetical gas increases to \[\sqrt{2}\] times when compressed adiabatically to half the volume. Its equation can be written as |
| A. | \[P{{V}^{3/2}}\]= constant |
| B. | \[P{{V}^{5/2}}\]= constant |
| C. | \[P{{V}^{7/3}}\]= constant |
| D. | \[P{{V}^{4/3}}\]= constant |
| Answer» B. \[P{{V}^{5/2}}\]= constant | |
| 8538. |
When connected across the terminals of a cell, a voltmeter measures 5V and a connected ammeter measures 10 A of current. A resistance of 2 ohms is connected across the terminals of the cell. The current flowing through this resistance will be [MP PMT 1997] |
| A. | 2.5 A |
| B. | 2.0 A |
| C. | 5.0 A |
| D. | 7.5 A |
| Answer» C. 5.0 A | |
| 8539. |
2 kg of ice at ? 20°C is mixed with 5 kg of water at 20°C in an insulating vessel having a negligible heat capacity. Calculate the final mass of water remaining in the container. It is given that the specific heats of water and ice are 1 kcal/kg per °C and 0.5 kcal/kg/°C while the latent heat of fusion of ice is 80 kcal/kg [IIT-JEE (Screening) 2003] |
| A. | 7 kg |
| B. | 6 kg |
| C. | 4 kg |
| D. | 2 kg |
| Answer» C. 4 kg | |
| 8540. |
A negatively charged plate has charge density of \[2\times {{10}^{-6}}C/{{m}^{2}}\]. The initial distance of an electron which is moving toward plate, cannot strike the plate, if it is having energy of \[200\,eV\] [RPET 1997] |
| A. | \[1.77\,mm\] |
| B. | \[3.51\,mm\] |
| C. | \[1.77\,cm\] |
| D. | \[3.51\,cm\] |
| Answer» B. \[3.51\,mm\] | |
| 8541. |
Two bodies of masses \[{{m}_{1}}\] and \[{{m}_{2}}\] are initially at rest at infinite distance apart. They are then allowed to move towards each other under mutual gravitational attraction. Their relative velocity of approach at a separation distance r between them is [BHU 1994; RPET 1999] |
| A. | \[{{\left[ 2G\frac{({{m}_{1}}-{{m}_{2}})}{r} \right]}^{1/2}}\] |
| B. | \[{{\left[ \frac{2G}{r}({{m}_{1}}+{{m}_{2}} \right]}^{1/2}}\] |
| C. | \[{{\left[ \frac{r}{2G({{m}_{1}}{{m}_{2}})} \right]}^{1/2}}\] |
| D. | \[{{\left[ \frac{2G}{r}{{m}_{1}}{{m}_{2}} \right]}^{1/2}}\] |
| Answer» C. \[{{\left[ \frac{r}{2G({{m}_{1}}{{m}_{2}})} \right]}^{1/2}}\] | |
| 8542. |
A shell is fired from a cannon with velocity v m/sec at an angle \[\theta \] with the horizontal direction. At the highest point in its path it explodes into two pieces of equal mass. One of the pieces retraces its path to the cannon and the speed in m/sec of the other piece immediately after the explosion is [IIT 1984; RPET 1999, 2001; UPSEAT 2002] |
| A. | \[3v\cos \theta \] |
| B. | \[2v\cos \theta \] |
| C. | \[\frac{3}{2}v\cos \theta \] |
| D. | \[\frac{\sqrt{3}}{2}v\cos \theta \] |
| Answer» B. \[2v\cos \theta \] | |
| 8543. |
The driver of a car travelling at velocity v suddenly see a broad wall in front of him at a distance d. He should [IIT 1977] |
| A. | Brake sharply |
| B. | Turn sharply |
| C. | (a) and (b) both |
| D. | None of the above |
| Answer» B. Turn sharply | |
| 8544. |
A wire has a mass \[0.3\pm 0.003\,g\], radius \[0.5\pm 0.005\,mm\] and length \[6\pm 0.06\,cm\]. The maximum percentage error in the measurement of its density is [IIT (Screening) 2004] |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» E. | |
| 8545. |
In hydrogen spectrum the wavelength of \[{{H}_{\alpha }}\] line is 656 nm whereas in the spectrum of a distant galaxy, \[{{H}_{\alpha }}\] line wavelength is 706 nm. Estimated speed of the galaxy with respect to earth is [IIT-JEE 1999; UPSEAT 2003] |
| A. | \[2\times {{10}^{8}}m/s\] |
| B. | \[2\times {{10}^{7}}m/s\] |
| C. | \[2\times {{10}^{6}}m/s\] |
| D. | \[2\times {{10}^{5}}m/s\] |
| Answer» C. \[2\times {{10}^{6}}m/s\] | |
| 8546. |
A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately |
| A. | 200 |
| B. | 100 |
| C. | \[\frac{200}{\sqrt{2}}\] |
| D. | 280 |
| Answer» C. \[\frac{200}{\sqrt{2}}\] | |
| 8547. |
In AM, the centpercent modulation is achieved when |
| A. | Carrier amplitude = signal amplitude |
| B. | Carrier amplitude ¹ signal amplitude |
| C. | Carrier frequency = signal frequency |
| D. | Carrier frequency ¹ signal frequency |
| Answer» B. Carrier amplitude ¹ signal amplitude | |
| 8548. |
A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in \[L{{i}^{++}}\] will be (Ionisation energy of hydrogen atom is 13.6eV) [UPSEAT 1999] |
| A. | 182.51 Å |
| B. | 177.17 Å |
| C. | 142.25 Å |
| D. | 113.74 Å |
| Answer» E. | |
| 8549. |
Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which one of the metal will be useful for the photoelectric cell working with visible light? (h = 6.6 ´ 10?34 J-s, c = 3 ´ 108 m/s) [DPMT 2003] |
| A. | Lithium |
| B. | Copper |
| C. | Both |
| D. | None of these |
| Answer» B. Copper | |
| 8550. |
A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region [IIT-JEE (Screening) 2000] |
| A. | Is zero |
| B. | Decreases as \[\frac{1}{r}\] |
| C. | Increases as r |
| D. | Decreases as \[\frac{1}{{{r}^{2}}}\] |
| Answer» C. Increases as r | |