CBSE Class 12 Physics Board Exam 2020: Check Important Questions

Check important questions for Class 12th Physics board exam 2020. This paper is scheduled on 2nd February 2020. In this article, you will also get other important resources for the preparation of the upcoming CBSE 12th Physics board exam 2020.

CBSE Class 12 Physics Board Exam 2020: Important 1 Mark Questions

Question: ________ is the current which can flow even in the absence of electric charge. 

Answer: Displacement current.

CBSE Sample Papers 2020 for 10th & 12th with Answers & Marking Schemes: All Subjects

CBSE 12th Physics Board Exam 2020: Important Resources & Tips for Last Minute Revision

Question: The SI unit of the electric polarization vector P is  _____

Answer: C/m².

Question: The electromagnetic wave that is widely used as a diagnostic tool in medicine is __________

Answer: X - rays.

Question: Two particles have equal momenta then the ratio of their de-Broglie wavelengths is ___________

Answer: 1:1 

CBSE Board Exam 2020: Check 3 Important Formats for Writing Good Answers

Question: A charge q is placed at the point of intersection of body diagonals of a cube. The

electric flux passing through any one of its faces is 

(a) q/(6εo)

(b) 3q/εo

(c) 6q/εo

(d) q/3εo

Answer: (a)

Question: The electric potential of earth is taken to be zero because earth is a good

(a) Insulator 

(b) conductor 

(c) semiconductor 

(d) dielectric 

Answer: (b)

Question: If the ammeter in the given circuit shown in the diagram reads 2A, the resistance R is

1Ω 

2Ω 

3Ω 

4Ω

Answer: (a)

Question: The heat produced by 100W heater in 2 minutes is equal to

10.5kJ 

16.3kJ 

12.0kJ 

14.2kJ 

Answer:(c)

Question: Time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of

speed of the particle 

mass of the particle

charge of the particle 

magnetic field 

Answer: (a)

Question: The final image formed in an astronomical refracting telescope with respect to the object is

Real inverted 

Real erect 

Virtual erect 

Virtual inverted 

Answer: (d)

Question: The shape of the interference fringes in Young’s double slit experiment when D (distance between slit and screen) is very large as compared to fringe width is nearly

straight line 

parabolic 

circular 

hyperbolic

Answer: (a)

Question: Unpolarized light is incident on a plane glass surface having refractive index . The angle of incidence at which reflected and refracted rays would become perpendicular to each other is : 

(a) 15° 

(b) 30° 

(c) 45° 

(d) 60° 

Answer: (d)

Question: Photoelectric emission from a given surface of metal can take place when the value of a ‘physical quantity’ is less than the energy of incident photon. The physical quantity is :

(a) Threshold frequency 

(b) Work function of surface

(c) Threshold wavelength 

(d) Stopping Potential 

Answer: (b) work function 

Question: A photon beam of energy 12.1eV is incident on a hydrogen atom. The orbit to which electron of H-atom be excited is

(a) 2nd 

(b) 3rd 

(c) 4th 

(d) 5th

Answer: (b)

Question: An equilateral prism is made up of material of refractive index . The angle of minimum deviation of light passing through the prism is_________. 

Answer: 60° 

Question: An electron is accelerated through a potential difference of 100 V , then de-Broglie wavelength associated with it is approximately ____________angstrom

Answer:1.227 angstrom

Question: If the angular speed of the armature of a dynamo is doubled then the amplitude of

the induced e.m.f will become_______. 

Answer: double 

Question: The magnetic flux linked with a coil changes by 2×10-2 Wb when the current

changes by 0.01A. The self inductance of the coil is_______. 

Answer: 2 H

Question: Horizontal and vertical components of earth’s magnetic field at a place are equal.

The angle of dip at that place is ________.

Answer: 45^o 

Question: A free floating magnetic needle at North pole is __________to the surface of earth. 

Answer: Vertical 

CBSE Class 12 Physics Board Exam 2020: Important 2 Marks Questions

Question: A 9 V battery is connected in series with a resistor .The terminal voltage is found to be 8 V. Current through the circuit is measured as 5 A. What is the internal resistance of the battery?

Answer: 0.2 ohm

Question: (i) Write two characteristics of a material used for making permanent magnets. (ii) Why is core of an electromagnet made of ferromagnetic materials?

Question: How does a charge q oscillating at certain frequency produce electromagnetic waves?

Question: How will the angular separation and visibility of fringes in Young’s double slit experiment change when (i) screen is moved away from the plane of the slits, and (ii) width of the source slit is increased?

Question: Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?

Question: An α - particle and a proton are accelerated through same potential difference. Find the ratio (vα/ vp)of velocities acquired by two particles.

Question: What is Brewster’s angle? Derive relation between Brewster angle and refractive index of medium which produces Plane Polarized light. 

Question: Energy gap in a p – n photodiode is 2.8 eV. Can it detect a wavelength of 6000 nm? Justify your answer. 

Question: Derive an expression for the radius of nth Bohr’s orbit in Hydrogen atom. 

CBSE Class 12 Physics Board Exam 2020: Important 3 Marks Questions

Question: Using Biot-Savart’s law, derive an expression for magnetic field at any point on axial line of a current carrying circular loop. Hence, find magnitude of magnetic field intensity at the centre of circular coil. 

Question: Obtain the resonant frequency and Q – factor of a series LCR circuit with L = 3H, C = 27𝛍F, R = 7.4Ω. It is desired to improve the sharpness of resonance of

circuit by reducing its full width at half maximum by a factor of 2. Suggest a suitable way. 

Question: Define resolving power of an astronomical refracting telescope and write

expression for it in normal adjustment.Assume that light of wave length 6000Å is

coming from a star, what is the limit of resolution of a telescope whose objective

has a diameter of 2.54m?

Question: Write the basic assumptions used in the derivation of lens – maker’s formula and hence derive this expression. 

Question:Suggest an idea to convert a full wave bridge rectifier to a half wave rectifier by changing the connecting wire/s. Draw the diagram and explain your answer. 

Question: A particle, having a charge +5 μC, is initially at rest at the point x = 30 cm on the x axis. The particle begins to move due to the presence of a charge Q that is kept fixed at the origin. Find the kinetic energy of the particle at the instant it has moved 15 cm from its initial position if (a) Q =+15μC and (b) Q = -15μC

Question:  Two material bars A and B of equal area of cross-section, are connected in series to a DC supply. A is made of usual resistance wire and B of an n-type semiconductor.

(a) In which bar is drift speed of free electrons greater?

(b) If the same constant current continues to flow for a long time, how will the voltage

drop across A and B be affected? Justify each answer. 

CBSE Class 12 Physics Board Exam 2020: Important 5 Marks Questions

Question: (a)Draw a ray diagram of compound microscope for the final image formed at least distance of distinct vision?

(b) An angular magnification of 30X is desired using an objective of focal length 1.25 cm and an eye piece of focal length 5 cm. How will you set up the compound microscope for the final image formed at least distance of distinct vision?

Question: (a) Draw a ray diagram of an astronomical telescope for the final image formed at least distance of distinct vision?

(b) An astronomical telescope has an angular magnification of magnitude 5 for distant objects. The separation between the objective and an eye piece is 36 cm and the final image is formed at infinity. Calculate the focal length of the objective and the focal length of the eye piece? 

Question: Derive mirror equation for a convex mirror. Using it, show that a convex mirror always produces a virtual image, independent of the location of object.

Question: (a) Draw a ray diagram for final image formed at distance of distinct vision (D) by a compound microscope and write expression for its magnifying power.

(b) An angular magnification (magnifying power) of 30x is desired for a compound

microscope using as objective of focal length 1.25cm and eye piece of focal

length 5cm. How will you set up the compound microscope? 

Question: Write the working principle of cyclotron and with a suitable diagram explain its working. Give any two applications of cyclotron.