CBSE 2015 Physics Question Paper for Class 12

About this paper

This is the CBSE Class 12 Physics (Theory) question paper from the 2015 board examination, Series SSO, Set 3, code 55/3/P. It carries 70 marks over three hours and has 26 compulsory questions in five sections: five one-mark questions, five two-mark questions, twelve three-mark questions, one four-mark value-based question and three five-mark long answers. The value-based question describes a boy named Anuj stopping his friends from lifting a live wire that fell during a thunderstorm. Internal choices are given in one two-mark question, one three-mark question and all three five-mark questions, and the physical constants are printed on the paper. This copy has the questions only, without answers.

Exam

CBSE Class 12

Subject

Physics

Year

2015

Paper code

55/3/P

Maximum marks

70

Time allowed

3 hours

Questions

26

Pages

17

Answers included

No, questions only

Paper pattern

• Section A

  5 marks

  Questions 1–5, one mark each

• Section B

  10 marks

  Questions 6–10, two marks each; internal choice in one

• Section C

  36 marks

  Questions 11–22, three marks each; internal choice in one

• Section D

  4 marks

  Question 23, a four-mark value-based question

• Section E

  15 marks

  Questions 24–26, five marks each, each with an internal choice

Topics covered

• Electrostatics and capacitors
• Current electricity, meter bridge and potentiometer
• Moving charges and magnetism
• Electromagnetic induction and AC
• Electromagnetic waves
• Ray optics and optical instruments
• Wave optics and polarisation
• Dual nature of radiation and matter
• Atoms and radioactive decay
• Semiconductors and Zener diode
• Communication systems

Questions from this paper

1. The equivalent wavelength of a moving electron has the same value as that of a photon of energy 6 × 10⁻¹⁷ J. Calculate the momentum of the electron.
2. Calculate the speed of light in a medium whose critical angle is 45°. Does the critical angle for a given pair of media depend on the wavelength of incident light?
3. In a coil of self-inductance 5 mH, the current changes from 4 A to 1 A in 30 ms. Calculate the emf induced in the coil.
4. The half-life of a certain radioactive material against α-decay is 100 days. After how much time will the undecayed fraction of the material be 6.25%?
5. Why can a bird sit on a suspended live wire without any harm, whereas touching it while standing on the ground can give a fatal shock?
6. Use Huygens' principle to show the propagation of a plane wavefront from a denser medium to a rarer medium, and hence find the ratio of the speeds of the wavefronts in the two media.