ISC 2025 Physics Improvement Examination Question Paper for Class 12

About this paper

This is ISC Class 12 Physics Paper 1 (Theory) from CISCE's 2025 Improvement Examination (paper code 861A, printed as 1225-861A-IE). It carries 70 marks, runs for three hours plus fifteen minutes of reading time, and has 20 compulsory questions in four sections, with internal choices in two questions each in Sections B, C and D. Section A has seven multiple-choice items, two of them assertion–reason, and seven very short answers. Section C includes a case where a student answers an examiner's questions on the double slit experiment, and Section D ends with a passage-based question on semiconductor devices, LEDs and rectifiers. A list of useful constants is printed at the end, and a simple scientific calculator is allowed.

Exam

ISC Class 12

Subject

Physics

Year

2025

Paper code

861A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

20

Pages

12

Answers included

No, questions only

Paper pattern

• Section A

  14 marks

  Question 1 with 14 one-mark parts: 7 multiple-choice (two assertion–reason) and 7 very short answers

• Section B

  14 marks

  Questions 2–8, two marks each; internal choice in two questions

• Section C

  27 marks

  Questions 9–17, three marks each; internal choice in two questions

• Section D

  15 marks

  Questions 18–20, five marks each, ending with a passage-based question on semiconductor devices; internal choice in two questions

Topics covered

• Electrostatics, Gauss's law and electric dipole
• Capacitors and dielectrics
• Current electricity, Kirchhoff's laws and potentiometer
• Moving charges, galvanometers and Ampère's law
• Magnetic properties of materials
• Electromagnetic induction and alternating current
• Electromagnetic waves
• Ray optics, prisms and microscopes
• Wave optics, interference and diffraction
• Photoelectric effect
• Bohr model and nuclear physics
• Semiconductor devices and rectifiers

Questions from this paper

1. A parallel beam of monochromatic light of wavelength 450 nm is incident normally on a rectangular slit of width 0.9 μm. Calculate the angular width of the central bright band.
2. Using Ampère's circuital law, obtain an expression for the magnetic field B at a point at a perpendicular distance r from an infinitely long straight conductor carrying a current I.
3. Two convex lenses of focal lengths 1.5 cm and 5 cm are placed coaxially to form a compound microscope. When a pin is kept 1.6 cm from the objective, a virtual magnified image is formed 25 cm from the eyepiece. Calculate the length of the microscope.
4. Two identical thin convex lenses, each of optical power 2 D, are kept in contact with each other. Calculate the focal length of the combination.
5. When the current through a solenoid increases from 0 to 10 A in 0.2 s, an emf of 20 V is induced in it. Calculate the coefficient of self-inductance of the solenoid.
6. State Bohr's postulate of quantisation of angular momentum and show how it can be obtained from the wave nature of orbiting electrons.