Class 12 > PYQ PHYSICS > 2017 > Set 3

2017

History 1 Views

Q1
When are two objects just resolved ? Explain. How can the resolving power of a compound microscope be increased ? Use relevent formula to support your answer.

Q2
(a) What is the line of sight communication ?
(b) Why is it not possible to use sky waves for the transmission of T.V. signals? Up to what distance can a signal be transmitted using an antenna of height ‘h’ ?

Q3
An ɑ-particle and a proton are accelerated through the same potential difference. Find the ratio of their de Broglie wavelengths.

Q4
(a) State two important features of Einstein’s photoelectric equation.
(b) Radiation of frequency 1015 Hz is incident on two photosensitive surfaces P and Q. There is no photoemission from surface P. Photoemission occurs from surface Q but photoelectrons have zero kinetic energy. Explain these observations and find the value of work function for surface Q.

Q5
(a) Obtain the expression for the torque τ experienced by an electric dipole of dipole moment p in a uniform electric field, E.
(b)What will happen if the field were not uniform ?

Q6
Explain briefly with the help of necessary diagrams, the forward and the reverse biasing of a p-n junction diode. Also draw their characteristic curves in the two cases.

Q7
Two identical capacitors of 12 pF each are connected in series across a battery of 50 V. How much electrostatic energy is stored in the combination ? If these were connected in parallel across the same battery, how much energy will be stored in the combination now ? Also find the charge drawn from the battery in each case.

Q8
(a) Write the expression for the force F acting on a particle of mass m and charge q moving with velocity v in a magnetic field B. Under what conditions will it move in
(i) a circular path and
(ii) a helical path ?
(b) Show that the kinetic energy of the particle moving in magnetic field remains constant.

2
3
4