1. Xtra Edge February 2012 - Career Point
1. Xtra Edge February 2012 - Career Point 1. Xtra Edge February 2012 - Career Point
PHYSICS 1. The spectrum of hydrogen atom has many lines although hydrogen atom contain only one electron why ? 2. What happens to the frequency when light passes from one medium to another. 3. What are coherent sources of light 4. If the intensity of the incident radiation on a metal is doubled, what happens to the kinetic energy of the emitted photoelectrons. 5. Prove mathematically that the average power over a complete cycle of alternating current through an ideal inductor is zero. 6. Figure shows a branch of a circuit. Find out the value of potential difference between A and B. A 1A 2Ω + – 2V 1Ω B 7. Write the following radiations in an ascending order in respect of their frequencies : X–rays, microwaves, ultraviolet rays, radiowaves MOCK TEST PAPER-3 CBSE BOARD PATTERN CLASS # XII SUBJECT : PHYSICS , CHEMISTRY & MATHEMATICS Solutions will be published in same issue General Instructions : Physics & Chemistry • Time given for each subject paper is 3 hrs and Max. marks 70 for each. • All questions are compulsory. • Marks for each question are indicated against it. • Question numbers 1 to 8 are very short-answer questions and carrying 1 mark each. • Question numbers 9 to 18 are short-answer questions, and carry 2 marks each. • Question numbers 19 to 27 are also short-answer questions, and carry 3 marks each. • Question numbers 28 to 30 are long-answer questions and carry 5 marks each. • Use of calculators is not permitted. General Instructions : Mathematics • Time given to solve this subject paper is 3 hrs and Max. marks 100. • All questions are compulsory. • The question paper consists of 29 questions divided into three sections A, B and C. Section A comprises of 10 questions of one mark each. Section B comprises of 12 questions of four marks each. Section C comprises of 7 questions of six marks each. • All question in Section A are to be answered in one word, one sentence or as per the exact requirement of the question. • There is no overall choice. However, internal choice has been provided in 4 questions of four marks each and 2 question of six marks each. You have to attempt only one of the alternatives in all such questions. • Use of calculators is not permitted. 8. In a closed surface incoming flux and outgoing flux is 5 × 10 5 and 4 × 10 5 V-m respectively then find out the charge enclosed by surface. 9. A freshly prepared radioactive substance of half life 2 hours emits radiation of intensity which is 64 times the permissible safe level. Find the minimum time after which it would possible to work with this source safely. 10. Why does the conductivity of a semiconductor change with the rise in temperature. 11. In optical fiber refractive index of cladding is less than core. Why ? 12. Where should an object be placed from a convex lens to from an image of the same size ? Can it happen in the case of a concave lens ? 13. A transmitting antenna at the top of tower has a height of 36 m and the height of the receiving antenna is 49 m. What is the maximum distance between them for satisfactory communication in the LOS mode ? (Radius of earth = 6400 km) XtraEdge for IIT-JEE 68 FEBRUARY 2012
14. Derive the expression for the capacitance of a parallel plate capacitor, having two identical plates each of area A and separated by a distance d, when the space between the plates is filled by a dielectric medium. 15. In a meter bridge shown in circuit diagram, the balance point is found to be at 40 cm from the end A when resistor Y is of value 20 Ω. Calculate the shifting in of balancing point on the same wire if X and Y are interchanged. X Y A D B G E 16. Two parallel wires of infinite length have linear charge densities λ1 and λ2 coulomb/metre. Derive an expression for force per unit length acting between them. 17. A 10 µF capacitor is charged by a 30 V d.c. supply and then connected across an uncharged 50 µF capacitor. Calculate (i) the final potential difference across the combination and (ii) the initial and final energies. How will you account for the difference in energy ? 18. Amplitude of electric field in an electromagnetic wave is 3×10 6 V/m. Find amplitude of magnetic field. 19. Explain it (i) work function (ii) Threshold frequency (iii) Threshold wave length (iv) Stopping potential 20. Show that the energy of the first excited state of He + atom is equal to the energy of the ground state of hydrogen atom 21. In a young's double slit experiment, the slits are separated by 0.56 mm and the screen is placed 2.8 m away. The distance between the central bright fringe and the fifth bright fringe is measured to be 1.5 cm. Determine the wavelength of light used in the experiment. 22. A communication system having operating wavelength λ in m can use only x% of its source frequency as its channel bandwidth. The system is to be used for transmitting TV signals requiring bandwidth of F Hz, How many channels can this system transmit simultaneously C 23. The given figure shows a network of resistances R1, R2, R3 and R4. Using Kirchhoff's laws, establish the balance condition for the network. B A G C XtraEdge for IIT-JEE 69 FEBRUARY 2012 R1 R2 R3 R4 D + – 24. Distinguish between resistance, reactance and impedance for an a.c. circuit. Draw graph showing variation for reactance of (i) a capacitor (ii) an inductor with frequency of the circuit. 25. A 0.5 m long metal rod PQ completes the circuit as shown. The area of the circuit is perpendicular to the magnetic field of flux density 0.15 T. If the resistance of the total circuit is 3 Ω. Calculate the force needed to move the rod in the direction as indicated with speed 2 ms –1 . × × × × × × Q × × × × × × × × × × × × × × × × × × × × × × × v × × × × × × × × × × × × × × × × × P × × × × 26. Explain the principle and working of cyclotron with the help of a labelled diagram. 27. Using Gauss' theorem, deduce an expression for the electric field intensity at any point due to a thin, infinitely long wire of charge/length λ C/m. 28. What is diffraction ? write down its difference with interference ? If single slit diffraction is obtained by using light of wavelength 5000Å and slit width 0.5 mm. Then calculate angular width of central maxima. OR What is dispersion ? How the angular dispersion is defined ? Which colours is deviated maximum by a prism ? Calculate dispersive power of crown glass if refractive indices for red, yellow and violet colours are 1.5140, 1.5170 and 1.5318 respectively. • 29. What is spectrum ? write down types of spectrum ? • OR • If electrons trans it from first excited state of H-atom to ground state and emitted radiations incidents over a metallic surface of threshold wavelength 4000 Å, then what is the value of
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PHYSICS<br />
<strong>1.</strong> The spectrum of hydrogen atom has many lines<br />
although hydrogen atom contain only one electron<br />
why ?<br />
2. What happens to the frequency when light passes<br />
from one medium to another.<br />
3. What are coherent sources of light<br />
4. If the intensity of the incident radiation on a metal is<br />
doubled, what happens to the kinetic energy of the<br />
emitted photoelectrons.<br />
5. Prove mathematically that the average power over a<br />
complete cycle of alternating current through an<br />
ideal inductor is zero.<br />
6. Figure shows a branch of a circuit. Find out the value<br />
of potential difference between A and B.<br />
A<br />
1A<br />
2Ω + –<br />
2V<br />
1Ω<br />
B<br />
7. Write the following radiations in an ascending order<br />
in respect of their frequencies :<br />
X–rays, microwaves, ultraviolet rays, radiowaves<br />
MOCK TEST PAPER-3<br />
CBSE BOARD PATTERN<br />
CLASS # XII<br />
SUBJECT : PHYSICS , CHEMISTRY & MATHEMATICS<br />
Solutions will be published in same issue<br />
General Instructions : Physics & Chemistry<br />
• Time given for each subject paper is 3 hrs and Max. marks 70 for each.<br />
• All questions are compulsory.<br />
• Marks for each question are indicated against it.<br />
• Question numbers 1 to 8 are very short-answer questions and carrying 1 mark each.<br />
• Question numbers 9 to 18 are short-answer questions, and carry 2 marks each.<br />
• Question numbers 19 to 27 are also short-answer questions, and carry 3 marks each.<br />
• Question numbers 28 to 30 are long-answer questions and carry 5 marks each.<br />
• Use of calculators is not permitted.<br />
General Instructions : Mathematics<br />
• Time given to solve this subject paper is 3 hrs and Max. marks 100.<br />
• All questions are compulsory.<br />
• The question paper consists of 29 questions divided into three sections A, B and C.<br />
Section A comprises of 10 questions of one mark each.<br />
Section B comprises of 12 questions of four marks each.<br />
Section C comprises of 7 questions of six marks each.<br />
• All question in Section A are to be answered in one word, one sentence or as per the exact requirement of the question.<br />
• There is no overall choice. However, internal choice has been provided in 4 questions of four marks each and<br />
2 question of six marks each. You have to attempt only one of the alternatives in all such questions.<br />
• Use of calculators is not permitted.<br />
8. In a closed surface incoming flux and outgoing flux<br />
is 5 × 10 5 and 4 × 10 5 V-m respectively then find out<br />
the charge enclosed by surface.<br />
9. A freshly prepared radioactive substance of half life<br />
2 hours emits radiation of intensity which is 64 times<br />
the permissible safe level. Find the minimum time<br />
after which it would possible to work with this<br />
source safely.<br />
10. Why does the conductivity of a semiconductor change<br />
with the rise in temperature.<br />
1<strong>1.</strong> In optical fiber refractive index of cladding is less<br />
than core. Why ?<br />
12. Where should an object be placed from a convex lens<br />
to from an image of the same size ? Can it happen in<br />
the case of a concave lens ?<br />
13. A transmitting antenna at the top of tower has a<br />
height of 36 m and the height of the receiving<br />
antenna is 49 m. What is the maximum distance<br />
between them for satisfactory communication in the<br />
LOS mode ?<br />
(Radius of earth = 6400 km)<br />
<strong>Xtra</strong><strong>Edge</strong> for IIT-JEE 68 FEBRUARY <strong>2012</strong>
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