# CBSE Class-12 Question Papers for IOP/Comptt Examination 2017 : Delhi Scheme, Physics ## CBSE Class-12 Question Papers for IOP/Comptt Examination 2017 : Physics, Set -1

PHYSICS (Theory)

Time allowed : 3 hours

Maximum Marks : 70

SECTION – A

1. Draw a plot showing variation of electric field with distance from the centre of a solid conducting sphere of radius R, having a charge of +Q on its surface.

2. State one factor which determines the intensity of light in the photon picture of light.

3. An iron-cored solenoid has self-inductance 2.8 H. When the core is removed, the self inductance become 2 mH. What is the relative permeability of the core used ?

4. An object is kept in front of a concave lens. What is the nature of the image formed ?

5.  When light travels from a rarer medium to denser medium, the speed of light decreases. Does the reduction in speed imply a reduction in the energy ?

SECTION – B

6. How is electromagnetic wave produced ? Draw a sketch of a plane e.m. wave propagating along X-axis depicting the directions of the oscillating electric and magnetic fields.

7.  A charge q of mass m is moving with a velocity of V, at right angles to a uniform magnetic field B. Deduce the expression for the radius of the circular path it describes.

8. Calculate the shortest wavelength of light emitted in the Paschen series of hydrogen spectrum. Which part of the electromagnetic spectrum, does it belong ? (Given : Rydberg constant, R = 1.1 × 107 m–1)

9. A small illuminated bulb is at the bottom of a tank, containing a liquid of refractive index u upto a height H. Find the expression for the diameter of an opaque disc, floating symmetrically on the liquid surface in order to cut-off the light from the bulb.
OR
A ray of light is incident on a glass prism of refractive index u and refracting angle A. If it just suffers total internal reflection at the other face, obtain an expression relating the angle of incidence, angle of prism and critical angle.

10. Depict the behaviour of magnetic field lines near (i) diamagnetic and (ii) paramagnetic substances. Justify, giving reasons.

SECTION – C

11.  Draw a graph showing the variation of de Broglie wavelength of a particle of charge q and mass m with the accelerating potential. Proton and deuteron have the same de Broglie wavelengths. Explain which has more kinetic energy.

12.  Explain the term, ‘amplitude modulation’ of a signal. For an amplitude modulated wave, the maximum amplitude is 10 V and the minimum amplitude is 2 V. Calculate the modulation index.

13.  State the Lorenz’s force and express it in vector form. Which pair of vectors are always perpendicular to each other ? Derive the expression for the force acting on a current carrying conductor of length L in a uniform magnetic field ‘B’.

14.  An optical instrument uses eye-lens of power 16 D and objective lens of power 50 D  and has a tube length of 16.25 cm. Name the optical instrument and calculate its magnifying power if it forms the final image at infinity.