Physics Chapter on Quantum Mechanics

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Questions and Answers

When a p-n junction diode is forward biased, then:

the depletion region is reduced and barrier height is increased

the depletion region is widened and barrier height is reduced (correct)

both the depletion region and barrier height are increased

both the depletion region and barrier height are reduced

Energy levels A, B and C of a certain atom correspond to increasing values of energy, i.e. $E_A < E_B < E_C$. If $\lambda_1$, $\lambda_2$ and $\lambda_3$ are the wavelengths of radiations corresponding to transitions C to B, B to A and C to A respectively, which of the following relations is correct?

$\lambda _3 = \lambda _1 + \lambda _2$

$\lambda _3 = \sqrt{\lambda _1 ^2 + \lambda _2 ^2}$

$\lambda _3 = \sqrt{\lambda _1 \lambda _2}$ (correct)

$\lambda _3 = rac{\lambda _1 \lambda _2}{(\lambda _1 + \lambda _2)}$

The energy that should be added to an electron to reduce its de-Broglie wavelength from 1 nm to 0.5 nm is

twice the initial energy (correct)

thrice the initial energy

four times the initial energy

equal to the initial energy

Assertion: Gamma rays are more energetic than X-rays. Reason: Gamma rays are of nuclear origin but X-rays are produced due to sudden deceleration of high energy electrons while falling on a metal of high atomic number.

both Assertion and Reason are true but Reason is not correct explanation of the Assertion (C) Signup and view all the answers

The binding energy per nucleon for deuterons ($^2_1H$) and helium ($^4_2He$) are 1.1 MeV and 7.0 MeV respectively. The energy released when two deuterons fuse to form a helium nucleus ($^4_2He$) is:

18.6 MeV (B) Signup and view all the answers

A Zener diode is connected to a battery and a load as shown below: The currents $I$, $I_z$ and $I_L$ are respectively

12.5 mA, 7.5 mA, 5 mA (A) Signup and view all the answers

In a H-atom spectrum $\lambda_{3-1}$ and $\lambda_{2-1}$ represents wavelengths emitted due to transition from second and first excited states to the ground state respectively. The value of $rac{\lambda_{3-1}}{\lambda_{2-1}}$ is:

27/32 (D) Signup and view all the answers

Maximum kinetic energy of a photoelectric varies with the frequency (f) of the incident radiation as

A (A) Signup and view all the answers

When a $U^{238}$ nucleus originally at rest, decays by emitting an alpha particle having a speed ' u', the recoil speed of the residual nucleus is

$rac{4u}{234}$ (C), $rac{4u}{234}$ (D) Signup and view all the answers

When 24.8 keV X-rays strike a material, the photoelectrons emitted from K shell are observed to move in a circle of radius 23 mm in a magnetic field of 2 10 T. The binding energy of K shell electrons is

7.4 keV (C) Signup and view all the answers

The truth table for the following logic circuit is:

B (A) Signup and view all the answers

A pulse of light of duration 100 ns is absorbed completely by a small object initially at rest. Power of the pulse is 30 mW and the speed of light is $3 imes 10^8$ ms. The final momentum of the object is

$3.0 imes 10^{-17} kg ms^{-1}$ (D) Signup and view all the answers

The wavelength of the first spectral line of sodium is 5896 . The first excitation potential of sodium atom will be (h = $6.63 imes 10^{-34} J s$)

2.1 V (D) Signup and view all the answers

Choose the incorrect statement.

The nuclear force becomes weak if the nucleus contains too many protons compared to the number of neutrons (C) Signup and view all the answers

In the following circuits, PN-junction diodes D1, D2 and D3 are ideal for the following potential of A and B, the correct increasing order of resistance between A and B will be (i) 10 V, 5 V (ii) -5 V, -10 V (iii) 4 V, 12 V

(i) = (iii) < (ii) (A) Signup and view all the answers

Study Notes

Question 1

Forward biasing a p-n junction reduces the depletion region and increases the barrier height.

Question 2

Energy levels (A, B, C) increase in order: EA < EB < Ec.
λ3 = (λ1 * λ2) / (λ1 + λ2)

Question 3

Energy to reduce de Broglie wavelength from 1 nm to 0.5 nm is twice the initial energy.

Question 4

Assertion: Gamma rays are more energetic than X-rays.
Reason: Gamma rays originate from nuclear processes, while X-rays result from high-energy electrons decelerating.
Both assertion and reason are true, and the reason correctly explains the assertion.

Question 5

Binding energy per nucleon for deuterons (H²) = 1.1 MeV
Binding energy per nucleon for helium (He⁴) = 7.0 MeV
Energy released when two deuterons fuse to form a helium nucleus = 23.6 MeV

Question 6

Uncertainty in velocity of an electron (v) = 0.005%
Velocity (v)= 50 ms⁻¹
Accuracy in measuring position (Δx) = 4.634 × 10⁻⁵m

Question 7

Zener diode connected to a battery and load.
Currents I, Iz, and I, respectively = 12.5 mA, 7.5 mA, 5 mA

Question 8

In a hydrogen atom spectrum, transitions from second and first excited states to the ground state are represented by values of 3-1 and 2-1.
Wavelength (3-1) = 32/27 (value provided)

Question 9

Maximum kinetic energy of photoelectric varies with frequency (f), represented by a graph. Graph shows linear increasing relationship.

Question 10

U²³⁸ nucleus at rest, decays by emitting an alpha particle with speed 'u'
Recoil speed of the residual nucleus = 4u/238

Question 11

24.8 keV X-rays strike a material.
Photoelectrons from K shell move in a circle (radius 23 mm) in a magnetic field (2 × 10⁻² T).
Binding energy of K shell electrons = 6.2 keV

Question 12

Truth table for a given logic circuit (involving inputs A and B, leading to output Y).

Question 13

A pulse of light (duration 100 ns).
Power of the pulse = 30 mW
Speed of light = 3 × 10⁸ ms⁻¹
Final momentum of the object = 9 × 10⁻¹⁷ kg ms⁻¹

Question 14

Wavelength of the first spectral line of sodium = 5896 Å
h = 6.63 × 10⁻³⁴ Js
First excitation potential of sodium atom = 2.1 V

Question 15

Nuclear force weakens with increasing number of protons, relative to neutrons, in the nucleus.
Nuclei with atomic numbers greater than 82 tend to disintegrate.
Nuclear force becomes stronger with more nucleons in the nucleus.

Question 16

Increasing order of resistance between A and B with different voltages:
(iii) < (ii) < (i)

Question 17

Electric displacement current through a surface area S is proportional to the rate of change of electric flux through S.

Question 18

Work functions of three photosensitive materials are 1 eV, 2 eV, and 3 eV, respectively.
Ratio of frequencies to produce photoelectrons of maximum kinetic energy of 1 eV from each of them is 3:2:1

Question 19

Compounds A and B are treated with dil. HCl to get Y and Z respectively.
Y (gas) turns acidified K₂Cr₂O₇ paper green..
Z turns lead acetate paper black.
X and Y are Na₂SO₃ and Na₂S, respectively

Question 20

Correct decreasing order of electropositive character among the elements (Fe, Sc, Rb, Br, Te, F, Ca).
- Rb > Ca > Sc > Fe > Te > Br > F

Question 1 (Numerical Physics)

Balmer series wavelengths (450 nm to 750 nm).
Work function = 2.0 eV
hc = 1242 eV nm

Question 2 (Numerical Physics)

Hydrogen-like atom (atomic number Z).
Excited state (quantum number 2n).
Maximum energy photon = 204 eV
Photon emitted in transition to quantum state n = 40.8 eV
Find atomic number Z.

Question 3 (Numerical Physics)

Nuclear radius ratio for an atom with mass number A and He⁴.

Question 4 (Numerical Physics)

Circuit current (in mA) through the Zener diode.

Question 5 (Numerical Chemistry)

Nuclear reaction (H² + H³ → He⁴).
Energy released per fusion reaction = 20 meV
Mass of H²¹ consumed per day = 0.1 g
Power of the reactor in MW.

Question 6 (Numerical Chemistry)

Number of compounds that do not act as Lewis acids.

Question 7 (Numerical Chemistry)

Oxidation number of Mn in the product of the alkaline oxidative fusion of MnO₂.

Question 8 (Numerical Chemistry)

Trends in the properties of group 16 hydrides (bond angle, volatility, thermal stability, acidic strength).

Question 9 (Numerical Chemistry)

Compounds that impart colour to a Bunsen flame.

Question 10 (Numerical Chemistry)

Number of B – O – B bonds in Na₂[B₄O₅(OH)₄]⋅8H₂O.
Number of B – B bonds.
Number of sp² hybridized B atoms.

Question 11 (Numerical Mathematics)

Shortest distance between two lines.

Question 12 (Numerical Mathematics)

Two lines intersect at a point.
Value of x² + 4.

Question 13 (Numerical Mathematics)

Coefficients of variation for two distributions are 60% and 75%.
Standard deviations are 18 and 15.
Arithmetic mean for the two distributions.

Question 14 (Numerical Mathematics)

Line passing through two points.
Line crosses the yz-plane.
Values of a and b.

Question 15 (Numerical Mathematics)

Line passing through a point with direction ratios.
Image of a point related to the line.
Length of median

Question 16 (Numerical Mathematics)

Points with position vectors (collinear).
Value of (19a - 6β)²

Question 17 (Numerical Mathematics)

Vectors a and b, and a vector related to vectors a + b and a - b.

Question 18 (Numerical Mathematics)

Direction cosines of two lines related by equations.
Angle between lines.

Question 19 (Numerical Mathematics)

Vectors a and b. Vector perpendicular to a +and a – b.

Question 20 (Numerical Mathematics)

Perpendicular distance of a point from a line.

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Description

Test your knowledge on key concepts in Quantum Mechanics with this quiz. Topics include p-n junctions, energy levels, de Broglie wavelength, gamma rays, binding energy, and uncertainty principles. Challenge yourself to grasp the intricate details of quantum phenomena.