CBSE Guess > Papers > Important Questions > Class XII > 2013 > Physics > index > Physics - by Mr. Ajay Yadav

CBSE CLASS XII

Physics

Short Type Questions (2 marks)

1. Name the reaction which takes place when a slow neutron beam strikes 92U235 nuclei. Write the nuclear reaction involved.
2. Define the terms 'Magnetic Dip' and 'Magnetic Declination' with the help of relevant diagrams.
3. Define 'electric line of force' and give its important properties.
4. State the condition under which the phenomenon of resonance occurs in a series LCR circuit. Plot a graph showing variation of current with frequency of a.c. source in a series LCR circuit.
5. How does the resistivity of
   1. a conductor and
   2. a semiconductor vary with temperature? Give reason for each case.
6. Explain how the width of depletion layer in a p-n junction diode changes when the junction is
   1. forward biased
   2. reverse biased.
7. Define resolving power of a compound microscope. How does the resolving power of a
   compound microscope change when
   1. refractive index of the medium between the object and objective lens increases?
   2. Wavelength of the radiation used is increased?
8. Write the relation for the force acting on a charge carrier q moving with a velocity through a magnetic field in vector notation. Using this relation, deduce the conditions under which this force will be
   1. maximum
   2. minimum.
9. You are given ‘a’ resistors, each of resistance ‘r’. These are first connected to get minimum possible resistance. In the second case, these are again connected differently to get maximum possible resistance. Compute the ratio between the minimum and maximum values of resistance so obtained.
10. Draw a circuit diagram using a metre bridge and write the necessary mathematical relation used to determine the value of an unknown resistance. Why cannot such an arrangement be used for measuring very low resistances?
11. What does the term LOS communication mean? Name the types of waves that are used for this communication. Which of the two-height of transmitting antenna and height of receiving antenna can affect the range over which this mode of communication remains effective?
12. Draw a ray diagram to show the refraction of light through a glass prism. Hence obtain the relation for the angle of deviation in terms of the angle of incidence, angle of emergence and the angle of the prism.
13. We do not choose to transmit an audio signal by just directly converting it to an e.m. wave of the same frequency. Give two reasons for the same.
14.  State Bohr’s postulate for the ‘permitted orbits’ for the electron in a hydrogen atom. Use this postulate to prove that the circumference of the nth permitted orbit for the electron can ‘contain’ exactly n wave lengths of the de Broglie wavelength associated with the electron in that orbit.
15. What is photoelectric effect? Drive Einstein’s photoelectric equation.
16. Explain the essential difference between interference and diffraction.
17. What is the basic difference between the atom or molecule of a diamagnetic and a paramagnetic material? Why are elements with even atomic number more likely to be diamagnetic?

Submitted By : Mr. Ajay Yadav
Email: [email protected]