Suppose a pure Si crystal has $5 \times 10^{28}$ atom $m ^{-3}$. It is doped by 1 ppm concentration of pentavalert As. Calculate the number of electrons and holes. (Given that $n_i=1.5 \times 10^{16} m^{-13}$ )
View full solution →Question types
MARCH 2024 question types
77 questions across 4 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.
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Sample Questions
MARCH 2024 questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
Write any two features of nuclear binding force.
A hydrogen atom initially in the ground level absorbs a photon which excites it to the $n=4$ level. Determine the wavelength and frequency of photon.
\[\left(h=6.625 \times 10^{-34} Js, c=3 \times 10^8 m / s\right)\]
View full solution →\[\left(h=6.625 \times 10^{-34} Js, c=3 \times 10^8 m / s\right)\]
Light of frequency $7.21 \times 10^{14} Hz$ is incident on a metal surface. Electrons with a maximum speed of $6.0 \times 10^5 m / s$ are ejected from the surface. What is the threshold frequency for photoemission of electrons?
\[\begin{array}{l}\left(h=6.625 \times 10^{-34} Js,\right. \\e=1.6 \times 10^{-19} C \\\left.m=9.1 \times 10^{-31} kg\right)\end{array}\]
View full solution →\[\begin{array}{l}\left(h=6.625 \times 10^{-34} Js,\right. \\e=1.6 \times 10^{-19} C \\\left.m=9.1 \times 10^{-31} kg\right)\end{array}\]
Using Huygens principle, explain reflection of a plane wave by a plane reflecting surface.
On the basis of Bohr's postulate obtain the formula for radius and total energy of electron in the $n^{\text {th }}$ stable orbit for hydrogen atom.
View full solution →Summarise any three experimental features and observation described in the experimental study of photoelectric effect.
Discuss the intensity of transmitted light when a polariod sheet is rotated between two crossed polaroids.
(a) The radii of curvatures of the faces of a double convex lens are 10 cm . and 15 cm . Its focal length is 12 cm . What is the refractive index of the material of lens?
(b) A convex lens of glass has 20 cm focal length in air. What is focal length in water? (Refractive index of air water is 1.33 . Refractive index of air-glass $=1.5$ )
View full solution →(b) A convex lens of glass has 20 cm focal length in air. What is focal length in water? (Refractive index of air water is 1.33 . Refractive index of air-glass $=1.5$ )
In actual transformers, small energy losses do occur. Give reason for it and how it can be reduce. (Any three)
Explain full wave rectification with the help of proper circuit diagram and draw the waveform of input and output voltage.
How long can an electric lamp of 100 W be kept glowing by fusion of 2.0 kg of deuterium? Take the fusion reaction as
\[{ }_1^2 H+{ }_1^2 H \longrightarrow{ }_2^3 He+n+3.27 MeV\]
\[{ }_1^2 H+{ }_1^2 H \longrightarrow{ }_2^3 He+n+3.27 MeV\]
Draw the ray diagram for the formation of image by a compound microscope and obtain the formula for magnification.
A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which $R =3 \Omega, L=25.48 mH$ and $C =796 \mu F$. Find
(a) the impedance of the circuit
(b) the phase difference between the voltage across the source and the current,
(c) the power dissipated in the circuit and
(d) the power factor.
View full solution →(a) the impedance of the circuit
(b) the phase difference between the voltage across the source and the current,
(c) the power dissipated in the circuit and
(d) the power factor.
As shown in figure, resistances are connected in the four arms of a Wheatstone bridge.
A galvanometer of $15 \Omega$ resistance is connected across BD. Calculate the current through galvanometer when a potential difference of 10 V is maintained across AC.
View full solution →A galvanometer of $15 \Omega$ resistance is connected across BD. Calculate the current through galvanometer when a potential difference of 10 V is maintained across AC.
If a conducting wire of length $L$ is uniformly stretched to double its length, then its conductivity becomes ___________ .
- Adouble
- B4 times
- Chalved
- ✓remain same
Answer: D.
View full solution →If a 12 pF capacitor is connected to a 50 V battery then the electrostatic energy stored in the capacitor is ___________.
- A$1.5 \times 10^{-12} J$
- B$1.5 \times 10^{-6} J$
- ✓$1.5 \times 10^{-8} J$
- D$3 \times 10^{-8} J$
Answer: C.
View full solution →Which of the following molecule is not polar?
- AHCl
- B$H _2 O$
- C$NH _3$
- ✓$H _2$
Answer: D.
View full solution →A charged capacitor is disconnected from the battery and if the distance between the two plates of the capacitor is increased then ___________ .
- ACharge on plate will decrease
- ✓Charge on plate will remain same
- CThe potential difference between the two plates will decrease
- DCapacitance of the capacitor will increase
Answer: B.
View full solution →By keeping a conductor in an external electric field and from the result obtained by electrostatics, which of the following options is wrong?
- AInside a conductor electrostatic field is zero
- BAt the surface of a charged conductor electric field must be perpendicular to the surface
- ✓The interior of the conductor have excess charge in static situation
- DElectrostatic potential is constant through out the volume of the conductor.
Answer: C.
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