Q. A plano convex lens of refractive index $\mu_1$ and focal length $f_1$ is kept in contact with another plano concave lens of refractive index $\mu_2$ and focal length $f_2$. If the radius of curvature of their spherical faces is R each and $f_1 = 2f_2$, then $\mu_1$ and $\mu_2$ are related as :

JEE Main JEE Main 2019

$\mu_1 + \mu_2 = 3$

$2 \mu_1 - \mu_2 = 1$

$2\mu_2 - \mu_1 = 1$

$3 \mu_2 - 2\mu_1 = 1$

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Questions from JEE Main 2019

1. In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $\lambda$ = 500 nm is incident on the slits.
The total number of bright fringes that are observed in the angular range $-30^{\circ} \le \theta \le 30^{\circ}$ is:

2. At a given instant, say t = 0, two radioactive substances A and B have equal activities. The ratio $\frac{R_B}{R_A}$ of their activities after time t itself decays with time t as $e^{-3t}$ . [f the half-life of A is $m_2$, the half-life of B is :

3. Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the value of $V_o$ changes by : (assume that the Ge diode has large breakdown voltage)

4. A rod of mass 'M' and length '2L' is suspended at its middle by a wire. It exhibits torsional oscillations; If two masses each of 'm' are attached at distance 'L/2' from its centre on both sides, it reduces the oscillation frequency by 20%. The value of ratio m/M is close to :

5. A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature $27^{\circ}C$. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled, is about :
[Take R = 8.3 J/ K mole]

6. A particle is executing simple harmonic motion (SHM) of amplitude A, along the x-axis, about x = 0. When its potential Energy (PE) equals kinetic energy (KE), the position of the particle will be :

7. A musician using an open flute of length 50 cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :

8. In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light $c = 3 \times 10^8 m/s,h = 6.6 \times 10^{-34} J-s)$

9. Two point charges $q_1( \sqrt{10} \mu C)$ and $q^2(-25 \; \mu C)$ are placed on the x-axis at x = l m and x = 4 m respectively. The electric field (in V/m) at a point y = 3 m on y-axis is, $\left[\text{take} \frac{1}{4\pi\varepsilon_{0}} = 9\times10^{9} Nm^{2} C^{-2}\right] $

10. A parallel plate capacitor with square plates is filled with four dielectrics of dielectric constants $K_1, K_2, K_3, K_4$ arranged as shown in the figure.
The effective dielectric constant K will be :

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1. An AC ammeter is used to measure current in a circuit. When a given direct current passes through the circuit, the AC ammeter reads 3 A. When another alternating current passes through the circuit, the AC ammeter reads 4 A. Then the reading of this ammeter, if DC and AC flow through the circuit simultaneously, is

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2. Assertion : Perspiration from human body helps in cooling the body
Reason : A thin layer of water on the skin enhances its emissivity.

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3. The speed of sound through oxygen at T K is v m$s^{-1}$. As the temperature becomes 2T and oxygen gas dissociates into atomic oxygen, the speed of sound

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4. If voltage across a bulb rated 220 volt-100 watt drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is

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5. If the dimensions of a physical quantity are given by $\ce{M^aL^bT^c}$, then the physical quantity will be

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6. There are 26 tuning forks arranged in the decreasing order of their frequencies. Each tuning fork gives 3 beats with the next. The first one is octave of the last. What is the frequency of 18th tuning fork?

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7. The electric resistance of a certain wire of iron is $R$. If its length and radius are both doubled, then

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8. A quarter horse power motor runs at a speed of 600 rpm. Assuming 40% efficiency, the work done by the motor in one rotation will be

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9. A cannon of mass I 000 kg, located at the base of an inclined plane fires a shelI of mass 100 kg in a horizontal direction with a velocity 180 $kmh^{-1}$. The angle of inclination of the inclined plane with the horizontal is 45$^{\circ}$. The coefficient of friction between the cannon and the inclined plane is 0.5. The height, in metre, to which the cannon ascends the inclined plane as a result of the recoiI is (g = 10 $ms^{-1})$

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10. Two charges $ q_1 $ and $q_2$ are placed 30 cm apart, as shown in the figure. A third charge $q_3$ is moved along the arc of a circle of radius 40cm from C to D. The change in the potential energy of the system is $ \frac{q_3}{ 4 \pi \varepsilon_0}$ k. where k is

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Q. A plano convex lens of refractive index $\mu_1$ and focal length $f_1$ is kept in contact with another plano concave lens of refractive index $\mu_2$ and focal length $f_2$. If the radius of curvature of their spherical faces is R each and $f_1 = 2f_2$, then $\mu_1$ and $\mu_2$ are related as :

$\mu_1 + \mu_2 = 3$

$2 \mu_1 - \mu_2 = 1$

$2\mu_2 - \mu_1 = 1$

$3 \mu_2 - 2\mu_1 = 1$

$\frac{1}{2f_{2}} = \frac{1}{f_{1}} =\left(\mu_{1} -1\right)\left(\frac{1}{\infty} - \frac{1}{-R}\right) $
$ \frac{1}{f_{2}} = \left(\mu_{2} -1\right) \left(\frac{1}{-R} - \frac{1}{\infty}\right) $
$ \frac{\left(\mu_{1}-1\right)}{R} = \frac{\left(\mu_{2}-1\right)}{2R} $
$2\mu_{2} -\mu_{2} = 1 $

Questions from JEE Main 2019

1. In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $\lambda$ = 500 nm is incident on the slits.
The total number of bright fringes that are observed in the angular range $-30^{\circ} \le \theta \le 30^{\circ}$ is:

2. At a given instant, say t = 0, two radioactive substances A and B have equal activities. The ratio $\frac{R_B}{R_A}$ of their activities after time t itself decays with time t as $e^{-3t}$ . [f the half-life of A is $m_2$, the half-life of B is :

3. Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the value of $V_o$ changes by : (assume that the Ge diode has large breakdown voltage)

4. A rod of mass 'M' and length '2L' is suspended at its middle by a wire. It exhibits torsional oscillations; If two masses each of 'm' are attached at distance 'L/2' from its centre on both sides, it reduces the oscillation frequency by 20%. The value of ratio m/M is close to :

5. A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature $27^{\circ}C$. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled, is about :
[Take R = 8.3 J/ K mole]

6. A particle is executing simple harmonic motion (SHM) of amplitude A, along the x-axis, about x = 0. When its potential Energy (PE) equals kinetic energy (KE), the position of the particle will be :

7. A musician using an open flute of length 50 cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :

8. In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light $c = 3 \times 10^8 m/s,h = 6.6 \times 10^{-34} J-s)$

9. Two point charges $q_1( \sqrt{10} \mu C)$ and $q^2(-25 \; \mu C)$ are placed on the x-axis at x = l m and x = 4 m respectively. The electric field (in V/m) at a point y = 3 m on y-axis is, $\left[\text{take} \frac{1}{4\pi\varepsilon_{0}} = 9\times10^{9} Nm^{2} C^{-2}\right] $

10. A parallel plate capacitor with square plates is filled with four dielectrics of dielectric constants $K_1, K_2, K_3, K_4$ arranged as shown in the figure.
The effective dielectric constant K will be :

Physics Most Viewed Questions

2. Assertion : Perspiration from human body helps in cooling the body
Reason : A thin layer of water on the skin enhances its emissivity.

3. The speed of sound through oxygen at T K is v m$s^{-1}$. As the temperature becomes 2T and oxygen gas dissociates into atomic oxygen, the speed of sound

4. If voltage across a bulb rated 220 volt-100 watt drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is

5. If the dimensions of a physical quantity are given by $\ce{M^aL^bT^c}$, then the physical quantity will be

6. There are 26 tuning forks arranged in the decreasing order of their frequencies. Each tuning fork gives 3 beats with the next. The first one is octave of the last. What is the frequency of 18th tuning fork?

7. The electric resistance of a certain wire of iron is $R$. If its length and radius are both doubled, then

8. A quarter horse power motor runs at a speed of 600 rpm. Assuming 40% efficiency, the work done by the motor in one rotation will be

10. Two charges $ q_1 $ and $q_2$ are placed 30 cm apart, as shown in the figure. A third charge $q_3$ is moved along the arc of a circle of radius 40cm from C to D. The change in the potential energy of the system is $ \frac{q_3}{ 4 \pi \varepsilon_0}$ k. where k is

Latest Updates

Q. A plano convex lens of refractive index $\mu_1$ and focal length $f_1$ is kept in contact with another plano concave lens of refractive index $\mu_2$ and focal length $f_2$. If the radius of curvature of their spherical faces is R each and $f_1 = 2f_2$, then $\mu_1$ and $\mu_2$ are related as :

$\mu_1 + \mu_2 = 3$

$2 \mu_1 - \mu_2 = 1$

$2\mu_2 - \mu_1 = 1$

$3 \mu_2 - 2\mu_1 = 1$

$\frac{1}{2f_{2}} = \frac{1}{f_{1}} =\left(\mu_{1} -1\right)\left(\frac{1}{\infty} - \frac{1}{-R}\right) $ $ \frac{1}{f_{2}} = \left(\mu_{2} -1\right) \left(\frac{1}{-R} - \frac{1}{\infty}\right) $ $ \frac{\left(\mu_{1}-1\right)}{R} = \frac{\left(\mu_{2}-1\right)}{2R} $ $2\mu_{2} -\mu_{2} = 1 $

Questions from JEE Main 2019

1. In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $\lambda$ = 500 nm is incident on the slits. The total number of bright fringes that are observed in the angular range $-30^{\circ} \le \theta \le 30^{\circ}$ is:

2. At a given instant, say t = 0, two radioactive substances A and B have equal activities. The ratio $\frac{R_B}{R_A}$ of their activities after time t itself decays with time t as $e^{-3t}$ . [f the half-life of A is $m_2$, the half-life of B is :

3. Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the value of $V_o$ changes by : (assume that the Ge diode has large breakdown voltage)

4. A rod of mass 'M' and length '2L' is suspended at its middle by a wire. It exhibits torsional oscillations; If two masses each of 'm' are attached at distance 'L/2' from its centre on both sides, it reduces the oscillation frequency by 20%. The value of ratio m/M is close to :

5. A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature $27^{\circ}C$. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled, is about : [Take R = 8.3 J/ K mole]

6. A particle is executing simple harmonic motion (SHM) of amplitude A, along the x-axis, about x = 0. When its potential Energy (PE) equals kinetic energy (KE), the position of the particle will be :

7. A musician using an open flute of length 50 cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :

8. In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light $c = 3 \times 10^8 m/s,h = 6.6 \times 10^{-34} J-s)$

9. Two point charges $q_1( \sqrt{10} \mu C)$ and $q^2(-25 \; \mu C)$ are placed on the x-axis at x = l m and x = 4 m respectively. The electric field (in V/m) at a point y = 3 m on y-axis is, $\left[\text{take} \frac{1}{4\pi\varepsilon_{0}} = 9\times10^{9} Nm^{2} C^{-2}\right] $

10. A parallel plate capacitor with square plates is filled with four dielectrics of dielectric constants $K_1, K_2, K_3, K_4$ arranged as shown in the figure. The effective dielectric constant K will be :

Physics Most Viewed Questions

2. Assertion : Perspiration from human body helps in cooling the body Reason : A thin layer of water on the skin enhances its emissivity.

3. The speed of sound through oxygen at T K is v m$s^{-1}$. As the temperature becomes 2T and oxygen gas dissociates into atomic oxygen, the speed of sound

4. If voltage across a bulb rated 220 volt-100 watt drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is

5. If the dimensions of a physical quantity are given by $\ce{M^aL^bT^c}$, then the physical quantity will be

6. There are 26 tuning forks arranged in the decreasing order of their frequencies. Each tuning fork gives 3 beats with the next. The first one is octave of the last. What is the frequency of 18th tuning fork?

7. The electric resistance of a certain wire of iron is $R$. If its length and radius are both doubled, then

8. A quarter horse power motor runs at a speed of 600 rpm. Assuming 40% efficiency, the work done by the motor in one rotation will be

10. Two charges $ q_1 $ and $q_2$ are placed 30 cm apart, as shown in the figure. A third charge $q_3$ is moved along the arc of a circle of radius 40cm from C to D. The change in the potential energy of the system is $ \frac{q_3}{ 4 \pi \varepsilon_0}$ k. where k is

Latest Updates

$\frac{1}{2f_{2}} = \frac{1}{f_{1}} =\left(\mu_{1} -1\right)\left(\frac{1}{\infty} - \frac{1}{-R}\right) $
$ \frac{1}{f_{2}} = \left(\mu_{2} -1\right) \left(\frac{1}{-R} - \frac{1}{\infty}\right) $
$ \frac{\left(\mu_{1}-1\right)}{R} = \frac{\left(\mu_{2}-1\right)}{2R} $
$2\mu_{2} -\mu_{2} = 1 $

1. In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $\lambda$ = 500 nm is incident on the slits.
The total number of bright fringes that are observed in the angular range $-30^{\circ} \le \theta \le 30^{\circ}$ is:

5. A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature $27^{\circ}C$. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled, is about :
[Take R = 8.3 J/ K mole]

10. A parallel plate capacitor with square plates is filled with four dielectrics of dielectric constants $K_1, K_2, K_3, K_4$ arranged as shown in the figure.
The effective dielectric constant K will be :

2. Assertion : Perspiration from human body helps in cooling the body
Reason : A thin layer of water on the skin enhances its emissivity.