An equi$-$convex crown glass lens has a focal length $20 \ cm$ for violet rays. Here $\mu_{ v }=1.5 \ \mu_{ r }=1.47$. Its focal length for red rays is
- A$24.85 \ cm$
- B$20.82 \ cm$
- ✓$21.28 \ cm$
- D$22.85 \ cm$
Answer: C.
View full solution →Question types
MODEL PAPER 3 question types
38 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.
38
Questions
6
Question groups
5
Question types
01
M.C.Q (1 Marks)
12 Q→02Assertion (A) & Reason (B) MCQ
4 Q→032 Marks Questions
6 Q→043 Marks Question
8 Q→055 Marks Questions
6 Q→06Case study (4 Marks)
2 Q→Sample Questions
MODEL PAPER 3 questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
The output of the given circuit in Figure.
- Awould be like a half-wave rectifier with negative cycles in output
- Bwould be like a half-wave rectifier with positive cycles in output
- Cwould be like that of a full-wave rectifier
- Dwould be zero at all times
The magnitude of the electric field due to a point charge object at a distance of 4.0 m is $9 N / C$. From the same charged object the electric field of magnitude, $16 \frac{N}{ C }$ will be at a distance of
- A3m
- B1m
- C6m
- D2m
Phenomenon of bending of waves around corners of obstacle without a change in medium is called _________.
- Adiffraction
- Binterference
- Creflection
- Drefraction
The universal property among all substances is
- Aferromagnetism
- Bnon-magnetism
- Cdiamagnetism
- Dparamagnetism
Assertion (A): An electric lamp is connected in series with a long solenoid of copper with air core and then connected to ac source. If an iron rod is inserted in solenoid, the lamp will become dim.
Reason (R): If an iron rod is inserted in solenoid, the inductance of solenoid increases.
Reason (R): If an iron rod is inserted in solenoid, the inductance of solenoid increases.
- AAssertion and reason both are correct statements and reason is correct explanation for assertion.
- BAssertion and reason both are correct statements but reason is not correct explanation for assertion.
- CAssertion is correct statement but reason is wrong statement.
- DAssertion is wrong statement but reason is correct statement.
Assertion (A): Colours are seen in thin layers of oil on the surface of the water.
Reason (R): White light is composed of several colours.
Reason (R): White light is composed of several colours.
- ABoth A and R are true and R is the correct explanation of A.
- BBoth A and R are true but R is not the correct explanation of A.
- CA is true but R is false.
- DA is false but R is true.
Assertion (A): Two equipotential surfaces cannot cut each other.
Reason (R): Two equipotential surfaces cannot cut each other.
Reason (R): Two equipotential surfaces cannot cut each other.
- ABoth A and R are true and R is the correct explanation of A.
- BBoth A and R are true but R is not the correct explanation of A.
- CA is true but R is false.
- DA is false but R is true.
Assertion (A): If the frequency of the incident light on a metal surface is doubled, the kinetic energy of emitted electrons is more than doubled.
Reason (R): The metal will provide additional energy to the emitted photoelectron for light of higher frequency than that for lower frequency.
Reason (R): The metal will provide additional energy to the emitted photoelectron for light of higher frequency than that for lower frequency.
- ABoth A and R are true and R is the correct explanation of A.
- BBoth A and R are true but R is not the correct explanation of A.
- CA is true but R is false.
- DA is false but R is true.
A long straight wire carrying a current of $30$ A is placed in an external uniform magnetic field of $4.0 \times 10^{-4} T$ parallel to the current. Find the magnitude of the resultant magnetic field at a point $2.0 \ cm$ away from the wire.
View full solution →The maximum torque acting on a coil of effective area $0.04 m^2$ is $4 \times 10^{-8} Nm$ when the current in it is $100 \ pA$ . Find the magnetic induction in which it is kept.
View full solution →An $\alpha-$particle after passing through a potential difference of $2 \times 10^6 V$ falls on a silver foil. The atomic number of silver is $47 .$ Calculate $(i)$ the kinetic energy of the $\alpha$-particle at the time of falling on the foil $(ii)$ the kinetic energy of the $\alpha$-particle at a distance of $5 \times 10^{-14} m$ from the nucleus and $(iii)$ the shortest distance from the nucleus of silver to which the $\alpha-$particle reaches.
View full solution →Describe briefly, with the help of a diagram, the role of the two important processes involved in the formation of a p-n junction.
Two identical bars, one of paramagnetic material and other of diamagnetic material are kept in a uniform external magnetic field parallel to it. Draw diagrammatically the modifications in the magnetic field pattern in each case.
A metallic rod of length l and resistance R is rotated with a frequency $\nu$ , with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius l, about an axis passing through the centre and perpendicular to the plane of the ring. A constant and uniform magnetic field B parallel to the axis is present everywhere.
i. Derive the expression for the induced emf and the current in the rod.
ii. Due to the presence of the current in the rod and of the magnetic field, find the expression for the magnitude and direction of the force acting on this rod.
iii. Hence obtain the expression for the power required to rotate the rod.
View full solution →i. Derive the expression for the induced emf and the current in the rod.
ii. Due to the presence of the current in the rod and of the magnetic field, find the expression for the magnitude and direction of the force acting on this rod.
iii. Hence obtain the expression for the power required to rotate the rod.
State Lenz's law. Give one example to illustrate this law. "The Lenz's law is a consequence of the principle of conservation of energy." Justify this statement.
In a Young's double experiment, the slits are $1.5 mm$ apart. When the slits are illuminated by a monochromatic light source and the screen is kept $1 m$ apart from the slits, width of $10$ fringes is measured as $3.93 \ mm.$
Calculate the wavelength of light used. What will be the width of $10$ fringes when the distance between the slits and the screen is increased by $0.5 m$. The source of light used remains the same.
View full solution →Calculate the wavelength of light used. What will be the width of $10$ fringes when the distance between the slits and the screen is increased by $0.5 m$. The source of light used remains the same.
The photon emitted during the de-excitation from the first excited level to the ground state of hydrogen atom is used to irradiate a photocathode of a photocell, in which stopping potential of 5 V is used. Calculate the work function of the cathode used.
The radionuclide ${ }^{11} C$ decays according to ${ }_6^{11} C \rightarrow{ }_5^{11} B+ e ^{+}+ v : T _{1 / 2}=20.3\ min$. The maximum energy of the emitted positron is $0.960 MeV$ . Given the mass values: $m \left({ }_6^{11} C \right)=11.011434 u$ and $m \left({ }_5^{11} B\right)=11.009305 u$, calculate $Q$ and compare it with the maximum energy of the positron emitted.
View full solution →$i$. What do you understand by the sharpness of resonance in a series $L-C-R$ circuit? Derive an expression for $Q$ factor of the circuit.
$ii$. Three electrical circuits having $AC$ sources of variable frequency are shown in the figures. Initially, the current flowing in each of these is same. If the frequency of the applied $AC$ source is increased, how will the current flowing in these circuits be affected? Give the reason for your answer.
View full solution →$ii$. Three electrical circuits having $AC$ sources of variable frequency are shown in the figures. Initially, the current flowing in each of these is same. If the frequency of the applied $AC$ source is increased, how will the current flowing in these circuits be affected? Give the reason for your answer.
$a.$ Show that an ideal inductor does not dissipate power in an ac circuit.
$b.$ The variation of inductive reactance $\left( X _{ L }\right)$ of an inductor with the frequency $( f )$ of the $ac$ source of $100 V$ and variable frequency is shown in the fig.
$i.$ Calculate the self$-$inductance of the inductor.
$ii.$ When this inductor is used in series with a capacitor of unknown value and a resistor of $10 \Omega$ at $300 s^{-1}$, maximum power dissipation occurs in the circuit. Calculate the capacitance of the capacitor.
View full solution →$b.$ The variation of inductive reactance $\left( X _{ L }\right)$ of an inductor with the frequency $( f )$ of the $ac$ source of $100 V$ and variable frequency is shown in the fig.
$i.$ Calculate the self$-$inductance of the inductor.
$ii.$ When this inductor is used in series with a capacitor of unknown value and a resistor of $10 \Omega$ at $300 s^{-1}$, maximum power dissipation occurs in the circuit. Calculate the capacitance of the capacitor.
$i.$ A Why does the electric field inside a dielectric slab decrease when kept in an external electric field?
$B.$ Derive an expression for the capacitance of a parallel plate capacitor filled with a medium of dielectric constant $K.$
$ii.$ A charge $q =2 \mu C$ is placed at the centre of a sphere of radius $20 \ cm $. What is the amount of work done in moving $4 \mu C$ from one point to another point on its surface?
$iii.$ Write a relation for polarisation $\overrightarrow{ P }$ of a dielectric material in the presence of an external electric field.
View full solution →$B.$ Derive an expression for the capacitance of a parallel plate capacitor filled with a medium of dielectric constant $K.$
$ii.$ A charge $q =2 \mu C$ is placed at the centre of a sphere of radius $20 \ cm $. What is the amount of work done in moving $4 \mu C$ from one point to another point on its surface?
$iii.$ Write a relation for polarisation $\overrightarrow{ P }$ of a dielectric material in the presence of an external electric field.
In Fig. the energy stored in $C _4$ is $27 J$ . Calculate the total energy stored in the system.
View full solution →$a.$ Use Huygen's geometrical construction to show how a plane wavefront at $t = 0$ propagates and produces a wavefront at a later time.
$b.$ Verify, using Huygen's principle, Snell's law of refraction of a plane wave propagating from a denser to a rarer medium.
$c.$ Illustrate with the help of diagrams the action of
$i.$ convex lens and
$ii.$ concave mirror, on a plane wavefront incident on it.
View full solution →$b.$ Verify, using Huygen's principle, Snell's law of refraction of a plane wave propagating from a denser to a rarer medium.
$c.$ Illustrate with the help of diagrams the action of
$i.$ convex lens and
$ii.$ concave mirror, on a plane wavefront incident on it.
Maxwell showed that the speed of an electromagnetic wave depends on the permeability and permittivity of the medium through which it travels. The speed of an electromagnetic wave in free space is given by $C=\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$ The fact led Maxwell to predict that light is an electromagnetic wave. The emergence of the speed of light from purely electromagnetic considerations is the crowning achievement of Maxwell’s electromagnetic theory. The The fact led Maxwell to predict that light is an electromagnetic wave. The emergence of the speed of light from purely electromagnetic considerations is the crowning achievement of Maxwell’s electromagnetic theory. The speed of an electromagnetic wave in any medium of permeability $\mu$ and permittivity $\varepsilon$ will be$\frac{c}{\sqrt{K \mu_r}}$ where K is the dielectric constant of the medium and $\mu_r$ is the relative permeability.
(i) The dimensions of $\frac{1}{2} \varepsilon_0 E^2$ ( $\varepsilon_0$ : permittivity of free space; $E =$ electric field $)$ is
(a) $MLT ^{-1}$ (b) $ML ^{-1} T^{-2}$ (c) $ML ^2 T^{-2}$ (d) $ML ^2 T^{-1}$
(ii) Let $\left[\varepsilon_0\right]$ denote the dimensional formula of the permittivity of the vacuum. If $M =$ mass, $L =$ length, $T =$ time and $A =$ electric current, then
(a) $\left[\varepsilon_0\right]= ML ^2 T^{-1}$
(b) $\left[\varepsilon_0\right]= MLT ^{-2} A^{-2}$
(c) $\left[\varepsilon_0\right]= M ^{-1} L^{-3} T^4 A^2$
(d) $\left[\varepsilon_0\right]= M ^{-1} L^{-3} T^2 A$
(iii) An electromagnetic wave of frequency 3 MHz passes from vacuum into a dielectric medium with permittivity $\varepsilon=4$. Then
(a) wavelength is halved and the frequency remains unchanged.
(b) wavelength and frequency both remain unchanged
(c) wavelength is doubled and the frequency remains unchanged
(d) wavelength is doubled and the frequency becomes half
OR
The electromagnetic waves travel with
(a) the speed of light $c =3 \times 10^8 m s ^{-1}$ in
(b) the speed of light $c =3 \times 10 m s ^{-1}$ in fluid medium. solid medium
(c) the speed of light $c =3 \times 10^8 m s ^{-1}$ in
(d) the same speed in all media free space
(iv) Which of the following are not electromagnetic waves?
cosmic rays, $\gamma$-rays, $\beta$-rays, X-rays
(a) $\beta$-rays (b) X-rays (c) $\gamma$-rays (d) cosmic rays
View full solution →(i) The dimensions of $\frac{1}{2} \varepsilon_0 E^2$ ( $\varepsilon_0$ : permittivity of free space; $E =$ electric field $)$ is
(a) $MLT ^{-1}$ (b) $ML ^{-1} T^{-2}$ (c) $ML ^2 T^{-2}$ (d) $ML ^2 T^{-1}$
(ii) Let $\left[\varepsilon_0\right]$ denote the dimensional formula of the permittivity of the vacuum. If $M =$ mass, $L =$ length, $T =$ time and $A =$ electric current, then
(a) $\left[\varepsilon_0\right]= ML ^2 T^{-1}$
(b) $\left[\varepsilon_0\right]= MLT ^{-2} A^{-2}$
(c) $\left[\varepsilon_0\right]= M ^{-1} L^{-3} T^4 A^2$
(d) $\left[\varepsilon_0\right]= M ^{-1} L^{-3} T^2 A$
(iii) An electromagnetic wave of frequency 3 MHz passes from vacuum into a dielectric medium with permittivity $\varepsilon=4$. Then
(a) wavelength is halved and the frequency remains unchanged.
(b) wavelength and frequency both remain unchanged
(c) wavelength is doubled and the frequency remains unchanged
(d) wavelength is doubled and the frequency becomes half
OR
The electromagnetic waves travel with
(a) the speed of light $c =3 \times 10^8 m s ^{-1}$ in
(b) the speed of light $c =3 \times 10 m s ^{-1}$ in fluid medium. solid medium
(c) the speed of light $c =3 \times 10^8 m s ^{-1}$ in
(d) the same speed in all media free space
(iv) Which of the following are not electromagnetic waves?
cosmic rays, $\gamma$-rays, $\beta$-rays, X-rays
(a) $\beta$-rays (b) X-rays (c) $\gamma$-rays (d) cosmic rays
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