Physics Outside Delhi Set 2 2022-2023 Science (English Medium) Class 12 Question Paper Solution

The ratio of the magnitudes of the electric field and magnetic field of a plane electromagnetic wave is ______.

1

`1/c`

c

`1/c^2`

Specify the transition of an electron in the wavelength of the line in the Bohr model of the hydrogen atom which gives rise to the spectral line of the highest wavelength ______.

n = 3 to n = 1

n = 3 to n = 2

n = 4 to n = 1

n = 4 to n = 2

A current of 0.8 A flows in a conductor of 40 Ω for 1 minute. The heat produced in the conductor will be ______.

1445 J

1536 J

1569 J

1640 J

A cell of emf E is connected across an external resistance R. When current 'I' is drawn from the cell, the potential difference across the electrodes of the cell drops to V. The internal resistance 'r' of the cell is ______.

`((E - V)/E)R`

`((E - V)/R)`

`((E - V)R)/I`

`((E - V)/V)R`

An isolated point charge particle produces an electric field `vecE` at a point 3 m away from it. The distance of the point at which the field is `vecE/4` will be ______.

2 m

3 m

4 m

6 m

A long straight wire of radius 'a' carries a steady current 'I'. The current is uniformly distributed across its area of cross-section. The ratio of the magnitude of magnetic field `vecB_1` at `a/2` and `vecB_2` at distance 2a is ______.

`1/2`

1

2

4

A steady current of 8 mA flows through a wire. The number of electrons passing through a cross-section of the wire in 10 s is ______.

4.0 × 10¹⁶

5.0 × 10¹⁷

1.6 × 10¹⁶

1.0 × 10¹⁷

Which one of the following elements will require the highest energy to take out an electron from them?

Pb, Ge, C and Si

Ge

C

Si

Pb

A conductor of 10 Ω is connected across a 6 V ideal source. The power supplied by the source to the conductor is ______.

1.8 W

2.4 W

3.6 W

7.2 W

Which one of the following metals does not exhibit emission of electrons from its surface when irradiated by visible light?

Rubidium

Sodium

Cadmium

Caesium

A hydrogen atom makes a transition from n = 5 to n = 1 orbit. The wavelength of photon emitted is λ. The wavelength of photon emitted when it makes a transition from n = 5 to n = 2 orbit is ______.

`8/7lambda`

`16/7lambda`

`24/7lambda`

`32/7lambda`

A photon of wavelength 663 nm is incident on a metal surface. The work function of the metal is 1.50 eV. The maximum kinetic energy of the emitted photoelectrons is ______.

3.0 × 10^-20 J

6.0 × 10^-20 J

4.5 × 10^-20 J

9.0 × 10^-20 J

In an extrinsic semiconductor, the number density of holes is 4 × 10²⁰ m^-3. If the number density of intrinsic carriers is 1.2 × 10¹⁵ m^-3, the number density of electrons in it is ______.

1.8 × 10⁹ m^-3

2.4 × 10¹⁰ m^-3

3.6 × 10⁹ m^-3

3.2 × 10¹⁰ m^-3

A ray of light of wavelength 600 nm propagates from air into a medium. If its wavelength in the medium becomes 400 nm, the refractive index of the medium is ______.

1.4

1.5

1.6

1.8

The formation of the depletion region in a p-n junction diode is due to ______.

movement of dopant atoms

diffusion of both electrons and holes

drift of electrons only

the drift of holes only

• Assertion (A): Work done in moving a charge around a closed path, in an electric field is always zero.
• Reason (R): Electrostatic force is a conservative force.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).

Assertion (A) is true and Reason (R) is false.

Assertion (A) is false and Reason (R) is also false.

• Assertion (A): In Young's double slit experiment all fringes are of equal width.
• Reason (R): The fringe width depends upon the wavelength of light (λ) used, the distance of the screen from the plane of slits (D) and slits separation (d).

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).

Assertion (A) is true and Reason (R) is false.

Assertion (A) is false and Reason (R) is also false.

In Young's double-slit experiment, the separation between the two slits is d and the distance of the screen from the slits is 1000 d. If the first minima fall at a distance d from the central maximum, obtain the relation between d and λ.

How are infrared waves produced?

Why are infra-red waves often called heat waves? Explain.

Give any two uses of infrared waves.

How are X-rays produced?

Write two uses of the following radiation.

X-rays

In the given figure the radius of curvature of the curved face in the planoconvex and the planoconcave lens is 15 cm each. The refractive index of the material of the lenses is 1.5. Find the final position of the image formed.

What happens to the interference pattern when two coherent sources are infinitely close?

What happens to the interference pattern when two coherent sources are far apart from each other?

What is meant by ionisation energy?

Write the ionisation energy value for the hydrogen atom.

What is mass defect?

How mass defect is related to the stability of the nucleus?

Draw an energy band diagram for a p-type semiconductor at T > 0 K.

A point object in the air is placed symmetrically at a distance of 60 cm in front of a concave spherical surface with a refractive index of 1.5. If the radius of curvature of the surface is 20 cm, find the position of the image formed.

A series RL circuit with R = 10 Ω and L = `(100/pi)` mH is connected to an ac source of voltage V = 141 sin (100 πt), where V is in volts and t is in seconds. Calculate

1. the impedance of the circuit
2. phase angle, and
3. the voltage drop across the inductor.

A ray of light is incident on a glass prism of refractive index µ and refracting angle A. If it just suffers total internal reflection at the other face, obtain a relation between the angle of incidence, angle of prism and critical angle.

A series CR circuit with R = 200 Ω and C = (50/π) µF is connected across an ac source of peak voltage ε₀ = 100 V and frequency v = 50 Hz. Calculate (a) impedance of the circuit (Z), (b) phase angle (Φ), and (c) voltage across the resistor.

Two cells of emf E₁ and E₂ and internal resistances r₁ and r₂ are connected in parallel, with their terminals of the same polarity connected together. Obtain an expression for the equivalent emf of the combination.

Distinguish between nuclear fission and fusion giving an example of each.

Explain the release of energy in nuclear fission and fusion on the basis of binding energy per nucleon curve.

How is the size of a nucleus found experimentally? Write the relation between the radius and mass number of a nucleus.

Answer the following question.

Show that the density of the nucleus is independent of its mass number A.

Use Gauss' law to derive the expression for the electric field `(vecE)` due to a straight uniformly charged infinite line of charge density λ C/m.

An infinitely long positively charged straight wire has a linear charge density λ. An electron is revolving in a circle with a constant speed v such that the wire passes through the centre, and is perpendicular to the plane, of the circle. Find the kinetic energy of the electron in terms of the magnitudes of its charge and linear charge density λ on the wire.

Draw a graph of kinetic energy as a function of linear charge density λ.

Consider two identical point charges located at points (0, 0) and (a, 0).

Is there a point on the line joining them at which the electric field is zero?

Consider two identical point charges located at points (0, 0) and (a, 0).

Is there a point on the line joining them at which the electric potential is zero?

Justify your answers for each case.

State the significance of the negative value of electrostatic potential energy of a system of charges.

Three charges are placed at the corners of an equilateral triangle ABC of side 2.0 m as shown in the figure. Calculate the electric potential energy of the system of three charges.

Define the coefficient of self-induction.

Derive the expression for the self-inductance of a long solenoid of cross sectional area A and length l, having n turns per unit length.

Calculate the self-inductance of a coil using the following data obtained when an AC source of frequency `(200/pi)` Hz and a DC source are applied across the coil.

With the help of a labelled diagram, describe the principle and working of an ac generator. Hence, obtain an expression for the instantaneous value of the emf generated.

The coil of an ac generator consists of 100 turns of wire, each of area 0.5 m². The resistance of the wire is 100 Ω. The coil is rotating in a magnetic field of 0.8 T perpendicular to its axis of rotation, at a constant angular speed of 60 radians per second. Calculate the maximum emf generated and power dissipated in the coil.

State Huygen's principle.

With the help of a diagram, show how a plane wave is reflected from a surface. Hence verify the law of reflection.

A concave mirror of focal length 12 cm forms three times the magnified virtual image of an object. Find the distance of the object from the mirror.

Draw a labelled ray diagram showing the image formation by a refracting telescope. Define its magnifying power.

Write two important limitations of a refracting telescope over a reflecting-type telescope.

The focal lengths of the objective and the eye-piece of a compound microscope are 1.0 cm and 2.5 cm respectively. Find the tube length of the microscope for obtaining a magnification of 300.

Read the following paragraph and answer the questions.

1. Explain the reason for the jumping of the ring when the switch is closed in the circuit.
2. What will happen if the terminals of the battery are reversed and the switch is closed? Explain.
3. Explain the two laws that help us understand this phenomenon.

Briefly explain various ways to increase the strength of the magnetic field produced by a given solenoid.

Read the following paragraph and answer the questions.

1. Which light beam has the highest frequency and why?
2. Which light beam has the longest wavelength and why?
3. Which light beam ejects photoelectrons with maximum momentum and why?

What is the effect of threshold frequency and stopping potential on increasing the frequency of the incident beam of light? Justify your answer.