Model Paper 3 — Physics STD 12 Science — Question

A person wishes to distinguish between two pillars located at a distance of 11km. What should be the minimum distance between these pillars (resolving power of normal human eye is 1')?

The collector plate in an experiment on photoelectric effect is kept vertically above the emitter plate. Light source is put on and a saturation photocurrent is recorded. An electric field is switched on which has a vertically downward direction.

Three capacitors of capacitances 3 μF, 9μF  and 18 μF  are connected once in series and another time in parallel. The ratio of equivalent capacitance in the two cases will be

(a) 1 : 15

(b) 15 : 1

(c) 1 : 1

(d) 1 : 3

In a compound microscope, if the objective produces an image I_o  and the eye piece produces an image I_e, then

(a) Io is virtual but Ie is real	(b) Io is real but Ie is virtual
(c) Io and Ie are both real	(d) Io and Ie are both virtual

The wavelength of X-rays decreases, when

(a) Temperature of target is increased

(b) Intensity of electron beam is increased

(c) K.E. of electrons striking the target is increased

(d) K.E. of electrons striking the target is decreased

The transistors provide good power amplification when they are used in

(a) Common collector configuration	(b) Common emitter configuration
(c) Common base configuration	(d) None of these

The idea of parmanu was given by:

The capacitance of an air capacitor is 15 μF the separation between the parallel plates is 6mm. A copper plate of 3mm  thickness is introduced symmetrically between the plates.  The capacitance now becomes

(a) 5 μF

(b) 7.5 μF

(c) 22.5 μF

(d) 30 μF

If the frequency of EM radiations is halved then the energy of EM radiation will become:

An ammeter with internal resistance 90 Ω reads 1.85 A when connected in a circuit containing a battery and two resistors 700 Ω and  410 Ω  in series. Actual current will be

(a) 1.85 A	(b) Greater than 1.85 A
(c) Less than 1.85 A	(d) None of these