1(a)vo/√2
(b)vo
(c ) vo/2
(d) √2 vo
V= Vo FOR 0≤ t ≤ T/2 V=0 FOR T/2 ≤ t ≤ T for a cycle . its rms value is
2) the ratio of maxium frequency and minium frequency of light emitted in balmer series of hydrogen spectrum in bohr’s model is
a) 11/9
b) 9/5
c) 11/7
d) 16/7
ans – a ) 9/5
3) at a certain temp in an intrinsic semiconductor the electron and hole concentration is 1.5 * 10 ¹⁶ m-3 , when it is doped with trivalent dopant hole concentration increases to 4.5 *
10 ²² m-3 in the doped semiconductor the concentration of electron will be
- 3* 10 ⁶ m-3
- 5* 10 ⁷ m-3
- 5 * 10 ⁹ m-3
- 6.75 * 10 ³⁸ m-3
Ans – c) 5 * 10 9 m-3
4) An infinitely long uniformly charged wire produces an electric field of 18 * 10 ⁴ N/c at a distance of 1cm .the linear charge density on the wire is
a) 1.12*10 ¯¹⁴ c/m
b)3.08 * 10 ¯15 c/m
c) 1 * 10 ¯⁹ c/m
d)1* 10 ¯⁷ c/m
ans 1* 10 ¯⁷ c/m
5) At o k , the resistivity of an intrinsic semiconductor is
a) same as that at 0°c
b) same as that at 300k
c) zero
d) infinite
ans – infinite
6)light of frequency 6.4 * 10¹⁴ HZ is incident on a metal of work function 2.14ev .the maxium kinetic energy of the emitted electron is about :
a)0.25ev
b)0.51ev
c)1.02ev
d)0.10ev
ans : b) o.51ev
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7)in an experiment on photoelectric effect the intensity of incident radiation is increased keeping the frequency remains same ,the no of photoelectron emitted will
a)increase b)decrease c)remains same d) depend on frequency
8)the si unit of mobility of charge carrier is
a)Ω s¯1 b)m² v ¯1 s ¯1
c)m s¯1 v¯1 d)Ω m
9) an inductor capacitor resistor are connected in series across an ac source of voltage .if the frequency of source decreased gradualy the reactance of
a) both the inductor and capacitor decreases
b) inductor decreases and capacitor increases
c) both inductor and capacitor increases
d) inductor increases and capacitor decreases
10) in moving coil galvanometer the deflecting torque acting on coil is related to current I flowing through it as
a)τ I ³ b) τ I ² c) τ I d) τ √I
11)in wave picture of light the intensity I of light is related to the amplitude A of wave as
a) I √A b) I A c) I A² d) I 1/A²
12)electromagnetic waves of wavelength of the order of few meter were first produced and detected in the laboratory by
a) j c Maxwell b) j c bose c) H R HERTZ D) G Marconi
13)the emf and internal resistance of a cell are E and r respectively. It is connected across an external resistance R = 2r . the potential drop across the terminal of the cell will be
a)E/4 B) E/2 C) 2E/3 D) E/3
14) in a single slit diffraction experiment , the width of the slit is halved . the width of the central maxium , in the diffraction pattern , will become :
a) half b) twice c) four times d) one fourth
15) which of the following graph correctly represents the variation of the magnitude of the magnetic fields outside a straight infinite current carrying wire of radius a , as a function of distance r from the centre of the wire ?
16) assertion(A) :when radius of the circular loop carrying a steady current is doubled , its magnetic moment becomes four times .
Reason (R) : the magnetic moment of a circular loop carrying a steady current is proportional to area of loop.
17) assertion(A): the nucleus x₃⁷ is more stable than the nucleus y₃ ⁴ .
Reason (R) : x₃⁷ contains more number of protons.
18) assertion(A):the internal resistance of cell is constsnt .
Reason (R) : ionic concentration of the electrolyte remains same during use of cell.
- Both assertion and reason are true and reason is the correct explanation of the assertion .
- Both assertion and reason are true and reason is not the correct explanation of the assertion .
- Assertion is true but reason is false
- Assertion is false and reason is also false .
19) how is the width of depletion layer of a pn junction diode affected when it is (1) forward biased (2) reverse biased ? justify your answers ?
20) explain the property of a pn junction which makes it suitable for rectifying alternating voltages . differentiate between a half wave and a full wave rectifier?
21) a)draw a graph showing the variation of binding energy per nucleon as a function of mass no A . the binding energy per nucleon for heavy nuclei (A>170) decreases with increase in mass no . explain ?
Or
b) using bohr ‘s postulate obtain the expression for radius of nth stable orbit in a hydrogen atom .
22) what is meant by the term displacement current ? briefly explain how the current is different from a conduction current ?
23)two wires of equal length are shaped in the form of a square loop and a circular loop. Both loops are suspended in a uniform magnetic field.prove that for same current the circular loop will experience large torque?
24) a) state Huygens principle . how did huygens explain the absence of backwave?
Or
b) use huygen’s principle to show reflection /refraction of a plane wave by 1) concave mirror 2) convex lens
25) The refractive indices of two media A and B are 2 and √2 respectively . what is the critical angle for their interface?
26) a)A particle of mass m and charge q is accelerated through a potential difference v . plot a graph of de Broglie wavelength λ associated with it as a function of V.
b) calculate the energy acquired by and de Broglie wavelength associated with ,an electron accelerated through a potential difference of 400v.
27) a) an ac source v=Vm sinωt is connected across an ideal capacitor .derive the expression for 1) current flowing in the circuit and 2) reactance of the capacitor . plot a graph of current I versus ωt.
Or
b) A series combination of an inductor L , a capacitor c and a resistor R is connected across an ac source of voltage in a circuit. Obtain an expression for the average power consumed by the circuit. Find power factor for 1) purely inductive circuit 2) purely resistive circuit.
28)a) i)prove that nuclear density is same for all nuclei.
ii) Draw a plot of potential energy of a pair of nucleons as a function of their separation . draw two inferences from this plot.
Or
b) i) draw a graph to show the variation of number of scattered particles detected (N) in Geiger – Marsden experiment as a function of scattering angle (Ф)
ii) Discuss briefly two conclusions that can be drawn from this graph and how they lead to the discovery of nucleus in an atom.
29)a rectangular loop of sides 25cm and 20cm is lying in x-y plane . it is subjected to a magnetic field B = (5t² + 2t + 10 ) ˄ķ , where B is in tesla and t is in seconds . if the resistance of the loop is 4 Ω , find the emf induced and the induced current in the loop at t= 5 s .
30) a potential difference v is applied across a load resistance R . v and R can be varied . if the current that flows in the circuit is I amp draw a plot showing the variation of power consumed by the resistor as a function of
a) R , keeping v constant
b) I , keeping R constant
c) v, keeping R constant
31) a) 1) write the principle and explain the working of moving coil galvanometer . a galvanometer as such cannot be used to measure the current in the circuit , why ?
2) why is the magnetic field made radial in a moving coil galvanometer ? how is it achieved ?
Or
b) 1) Derive an expression for magnetic field on the axis of current carrying circular loop ?
2) write any two point difference between a diamagnetic and a paramagnetic substance ?
32) (a) (i) Draw a ray diagram showing the formation of a real image of an object placed at a distance u in front of a concave mirror of radius of curvature R . hence obtain the relation for the image distance v in terms of u and R.
(ii) A 1.8 m tall person stands in front of a convex lens of focal length 1m , at a distance of 5 m . find the position and height of the image formed.
Or
b) (i)Draw a ray diagram showing refraction of a ray of light through a triangular glass prism. Hence obtain the relation for the refractive index (μ) in terms of angle of prism (A) and angle of minimum deviation (δ) .
(ii) The radii of curvature of the two surfaces of a concave lens are 20cm each. Find the refractive index of the material of the lens if its power is -5D.
33) (a) (i) Define electric flux and write its SI unit .
(ii) use gauss law to obtain the expression for the electric field due to a uniformly charged infinite plane sheet .
(iii) A cube of side L is kept in space as shown in the figure . An electric field E = (Ax + B ) N/C exists in the region. Find the net charge enclosed by the cube .
34) Diffraction of light is bending of light around the corner of an object whose size is compareable with the wavelength of light . diffraction actually defines the limits of ray optics . this limit for optical instrument is set by the wavelength of light . an experimental arrangement is set up to observe the diffraction pattern due to single slit .
Answer the following questions based on the above :
- How will the width of central maximum be affected if the wavelength of light is increased ?
- Under what condition is the first minimum obtained ?
- Write two points of difference between interference and diffraction patterns .
Or
- Two students are separated by a 7m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see eachother even though they can converse easily ?
35) A beam of electrons moving horizontally with a velocity of 3 * 10 7 m/s enter a region between two plates as shown in figure . A suitable potential difference is applied across the plates such that the electron beam just strikes the edge of the lower plate .
Answer the following questions based on the above :
a) how long does an electron take to strike the edge ?
b)what is the shape of the path followed by electron beam and why ?
c)find the potential difference applied ?
or
c) find the magnitude and direction of the magnetic field which should be created in the space between the plates so that the electron beam goes straight undeviated ?