## Tuesday, May 20, 2008

### IIT JEE SImple Harmonic Motion Practice Set - Physicsgoeasy Blog

http://physicsgoeasy.blogspot.com/2008/05/iitjee-test-series-for-shm.html

## Monday, May 19, 2008

### Electricity Practice set -from Physics go easy

17 question set

http://physicsgoeasy.blogspot.com/2008/05/iit-jee-test-serieselectricity-1.html

## Saturday, May 17, 2008

### Past JEE OQ - Wave Motion - Light Waves-1

Past JEE Objective Questions Wave Motion - Light Waves

Questions on light waves (Young’s double slit experiment)
1982
1. In Young’s double slit experiment the interference pattern is found to have an intensity ratio between bright and black fringes as 9. This implies that

a. the intensities due to the two slits are 5 units and 4 units respectively.
b. the intensities at the screen due to two slits are 4 units and 1 unit respectively.
c. the amplitude ratio is three.
d. the amplitude ratio is two.

1984
1. White light is used to illuminate the two slits in a Young’s double slit experiment. The separation between the slits is b and the screen is at a distance d (d>>b) from the slits. At a point on the screen directly in front of one of the slits, certain wavelengths are missing. Some of these missing wavelengths are

a. λ = b²/d
b. λ = 2b²/d
c. λ= b²/3d
d. λ= 2b²/3d

1986
1. In Young’s double slit experiment, the two slits act as coherent sources of equal amplitude A and of wavelength λ. In another experiment with the same set p the two slits are sources of equal amplitude A and wavelength λ, but are incoherent. The ratio of the intensity of light at the mid point of the screen in the first case to that in the second case is --------------.

1987
1. In a Young’s double slit experiment performed with a source of white light, only black and white fringes are observed.

1994
1. A beam of light of wavelength 600 nm from a distant source falls on a single slit of 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is

a. 1.2 cm
b. 1.2 mm
c. 2.4 cm
d. 2.4 mm

1995
1. In an interference arrangement similar to Young’s double-slit experiment, the slits S1 and S2 are illuminated with coherent microwave sources, each of frequency 10^6 Hz. The sources are synchronized to have zero phase difference. The slits are separated by a distance of d = 150 m. The intensity of I(θ) is measured as a function of θ, where θ is defined as shown in the figure*. If I0 is the maximum intensity, the I(θ) for 0≤ θ ≤90° is given by

a. I(θ) = I0/2 for θ = 30°
b. I(θ) = I0/4 for θ = 90°
c. I(θ) = I0 for θ = 0°
d. I(θ) is constant for all values of θ

*(θ is the angle between the line joining the mid point of slits and its image on the screen and the line joining the image on the screen with mid pint of the slits)

1998
1. A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of the slit is

a. 0
b. π/2
c. π
d. 2 π

1999.
1. Yellow light is used in a single slit diffraction experiment with slit width of 0.6 mm. If yellow light is replaced by X-rays, then the observed pattern will reveal

a. that the central maximum is narrower.
b. more number of fringes
c. less number of fringes
d. no diffraction pattern

2000
1. In a doble slit experiment, instead of taking slits of equal widths, one slit is made twice as wide as the other. Then, in the interference pattern

a. the intensities of both the maxima and minima increase.
b. the intensity of the maxima increases and the minima has zero intensity.
c. the intensity of the maxima decreases and that of the minima increases.
d. the intensity of the maxima decreases and the minima has zero intensity.

2001
1. In a Young’s double slit experiment, 12 fringes are observed to be formed in a certain segment of the screen when light of wavelength 600 nm is used. If the wavelength is changed to 400 nm, number of fringes observed in the same segment of the screen is given by

a. 12
b. 18
c. 24
d. 30

2002
1. In an ideal double slit experiment, when a glass plate (refractive index 1.5) of thickness t is introduced in the path of one of the interfering beams (wavelength λ), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass plate is
a. 2 λ
b. 2 λ/3
c. λ/3
d. λ

(optical path concept is to be used for this problem)

2004
1. In a Young’s double slit experiment, bichromatic light of wavelengths 400 nm and 560 nm are used. The distance between the slits is 0.1 mm and the distance between the slits and the screen is 1 m. The minimum distance between two minima is

a. 4 mm
b. 5.6 mm
c. 14 mm
d. 28 mm

2005
1. In a Young’s double slit experiment an electron beam is used to obtain interference pattern. If the speed of electrons decreased then

a. no interference pattern is observed.
b. distance between two consecutive fringes decreases
c. distance between two consecutive fringes increases.
d. distance between two consecutive fringes remains the same.

2. In a Young’s double slit experiment, the angular position θ of a bright fringe having intensity one fourth of the maximum intensity is given by

a. sin-1 (λ/4d)
b sin-1(λ/3d)
c. sin-1(λ/2d)
d. sin-1(λ/d)

(θ is the angle between the line joining the mid point of slits and its image on the screen and the line joining the image on the screen with mid pint of the slits)

## Monday, May 12, 2008

### Past JEE Objective Questions - Magnetism - Part 1

1982

1(viii) A magnetic needle is kept in a non uniform magnetic field. It experiences

a. a force and a torque
b. a force but not a torque
c. a torque but not a force
d. neither a force nor a torque

1983
1(viii) A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field (vector) B0 such that vector (B0) is perpendicular to the plane of the loop. The magnetic force acting on the loop is

a. irB0
b. 2 πirB0
c. zero
d. 2 πirB0

4(vii) state true or false.

There is no change in the energy of a charged particle moving in a magnetic field although a magnetic force is acting on it.

(viii) State whether the following statement is true or false
A charged particle enters a region of uniform magnetic field at angle of 85° to the magnetic lines of force. The path of the particle is circle.

1984

1(v) A proton with a constant velocity passes through a region of space without ny change in its velocity. If E and B represent the electric and magnetic fields respectively, this region of space may have:

a. E = 0, B = 0
b. E = 0, B ≠0
c. E≠0, B = 0
d. E≠0, B ≠0

3(vii) State whether the following statement is true or false.

An electron and a proton are moving with the same kinetic energy along the same direction. When they pass through a uniform magnetic field perpendicular to the direction of their motion, they describe circular paths of the same radius.

1986
1(vii) Two thin long parallel wires separated by a distance b are carrying a current i each. The magnitude of the force per unit length exerted by one wire on the other is

a. µ0i²/b²
b. µ0i²/2πb
c. µ0i/2πb
d. µ0i/2πb²

3(iv) State whether the following statement is true or false

A coil of metal wire is kept stationary in a non-uniform magnetic field. An emf is induced in the coil.

1987
2(ix) A wire of length L metres carrying a current i amperes is bent in the form of a circle. The magnitude of its magnetic moment is ----------------- in MKS units.

3(iv) State whether the following statement is true or false

A conducting rod AB (parallel to the Y-axis) moves parallel to the x-axis in a uniform magnetic field pointing in the positive z-direction. The end A of the rod gets positively charged.

1988

2(iv) Two particles of X and Y having equal charge, after being accelerated through the same potential difference enter a region of uniform magnetic field and describe circular paths of radii R1 and R2 respectively. The ratio of the mass of X to the mass of Y is

a. (R1/R2 1/2
b. R2/R1
c. (R1/R2)²
d. R1/R2

3(i) In the formual X = 3YZ², X and Z have dimensions of capacitance and magnetic induction respectively. The dimensions of Y in MKSQ system are-------------------

3(viii) The semicircular wireloop PQRSP is formed by joining two semicircular wires of radii R1 and R2. The radius of SP of the loop is R2 and the radius of RQ of the loop is R1 (R1

## Sunday, May 4, 2008

### Past JEE Objective Questions Modern Physics - Part 1

1982
1. The shortest wavelength of X-rays emitted from an X-ray tube depends on

a. the current in the tube
b. the voltage applied to the tube.
c. the nature of gas in the tube.
d. the atomic number of the target material.

2. the threshold wave length for photoelectric emission from a material is 5200 Angstrom. Photoelectrons will be emitted when this material is illuminated with monochromatic radiation from a

a. 50 watt red lamp.
b. 1 watt neon lamp.
c. 50 watt infrared lamp.
d. 1 watt untraviolet lamp.

1983
3. Beta rays emitted by a radioactive material are

b. electrons orbiting around the nucleus
c. charged particles emitted by the nucleus
d. neutral particles

4. If elements with principal quantum number n>4 were not allowed in nature, thenumber of possible elements would be

a. 64
b. 32
c. 4
d. 64

5. Consider the spectral line resulting from the transition n = 2 --> n =1 in the atoms and ions given below. The shortest wavelength is produced by

a. hydrogen atom
b. single ionized helium
c. deuteron atom
d. doubly ionized lithium

6. The equation 4[1,1]H+ --> {4,2]He2+ +2e++26 MeV represents

a. β decay
b. γ decay
c. fusion
d. fission

7. To produce characteristic X-rays using Tungsten target in an X-ray generator, the accelerator voltage should be greater than -----------volts and the energy of the characteristic radiation is ---------eV. (The binding energy of the innermost electrons in tungsten is 40 Kev.)

8. The radioactive decay rate of a radioactive element is found to be 10³ disintegrations/second at a certain time. If the half-life of the element is one second, the decay rate after one second is ------------- and after three seconds is -----------------.

9. Say whether the statement is true or false.
A small metal ball is suspended in a uniform electric field with the help of an insulation thread. If a high energy X-ray beam falls on the ball, the ball will be deflected in the direction of the field.

1984

10

11. Identify the correct statement(s).

In the Bohr model of the hydrogen atom
a. the radius of the nth orbit is proportional to n².
b. the total energy of the electron in the nth orbit is inversely proportional to n.
c. the angular momentum of the electron in an orbit is an integral multiple of h/2π .
d. the magnitude of the potential energy of the electron in any orbit is greater than its kinetic energy.

12. the maximum kinetic energy of electrons emitted in the photoelectric effect is linearly dependent on the ------------------- of the incident radiation.

13.

1985
14. A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, this region of space may have

a. E = 0,B =0
b. E = 0,B ≠0
c. E≠0, B = 0
d. E≠0, B≠0

15. The X-ray beam coming from an X-ray tube will be

a. monochromatic
b. having all wavelengths smaller than a certain maximum wavelengths.
c. having all wavelengths larger than a certain minimum wavelength.
d. having allwavelengths lying between a minimum and a maximum wavelength.

16. IN the uranium radioactive series the initial nucleus is [238,92]U and the final nuclues is [206,82]Pb. When the uranium nucleus decays to lead, the number of α-particles emitted is ------------ and the number of β-particles emitted is ---------.

17. Planck's constant has the dimensions -----------------.

1986

18. the mass number of a nucleus is

a. is always less than its atomic number.
b. always more than its atomic number.
c. sometimes equal to its atomic number.
d. sometimes more than and sometimes equal to its atomic number.

19. When the number of of electrons striking the anode of an X-ray tube is increased, the ----------- of the emitted X-rays increases, while when the speeds of the electrons striking the anode are increased, the cut-off wavelength of the emitted X-rays ----------------.

20. When Boron nucleus [10,5]B is bombarded by neutrons, α particles are emitted. The resulting nuclues is of the element ------------ and has the mass number ---------.

21. Atoms having the ---------- but different ----------- are called isotopes.

22. State whether the statement is true or false.
In a photoelectric emission process, the maximum energy of the photoelectrons increases with increasing intensity of the incident light.

### Past JEE Objective Questions Modern Physics - Part 2

1987

23. Four physical quantities are listed in column I. Their possible values are listed in column II in a random order. Match them.

ColumnI ----------------------Column II

a. Thermal energy of air----------e. 0.02 eV
molecules at room ----------------
temperature

b. Binding energy of--------------f. 2 eV
heavy nuclei per------------------
nucleon

c. X-ray photon energy-----------g. 1 keV

d. Photon energy of--------------h. 7 meV
visible light

24. Photoelectric effect supports quantum nature of light becasue

a. there is a minimum frequency of light.

b. the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity.

c. even when the metal surface is fairly illuminated, the photoelectrons leave the surface immediately.

d.electric charge of the photoelectrons is quantized.

25. During a negative beta decay

a.an atomic electron is ejected.
b. an electron which is already present within the nucleus is ejected.
c. a neutron in the nucleus decays emitting an electron.
d. a part of the binding energy of the nucleus is converted into an electron.

26. During nuclear fusion reaction;
a. a heavy nucleus breaks into two fragments by itself.
b. a light nucleus bombarded by thermal neutrons breaks up.
c. a heavy nucleus bombarded by thermal neutrons breaks up.
d. two light nuclei combine to give a heavier nucleus and possibly other products.

## Friday, May 2, 2008

### Past JEE Questions - Thermal Physics - Part 1

1984

1. At room temperature, the rms speed of the molecules of a certain diatomic gas is found to be 1930 m/s. The gas is

a. H2
b. F2
c. O2
d. Cl2

2. One mole of a monatomic ideal gas is mixed with one mole of a diatomic ideal gas. The molar heat capacity of the mixture at constant volume is ----------------.

3. 70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30°C to 35°C. the amount of heat required (in calories) to raise the temperature of same gas through the same range (30°c to 35°C) at constant volume is

a. 30
b. 50
c. 70
d. 90

1986

Steam at 100°C is passed into 1.1 kg of water contained in a calorimeter of water equivalent 0.02 kg at 15°C, till the temperatur of the calorimeter and its contents rises to 80°C. The mass of the steam condensed in kilogram is

a. 0.130
b. 0.065
c. 0.260
d. 0.135

1987

State true or false

At a given temperature, the specific heat capacity of a gas at constant pressure is always greater than its specific heat capacity at constant volume.

1988

State true of false. Give very brief reasons

Two spheres of the same material have radii 1m and r4m and temperatures 4000 K and 2000 K respectively. The energy radiated per second by the first sphere is greater than by the second.

1989

300 g of water at 25°C is added to 100 g of ice at 0°C. The final temperature of the mixture is -------------°C.

Identify all correct alternatives
For an ideal gas
a. The change in internal energy in a constant pressure process from temperature T1 to T2 is equal to nCv(T2-T1), when Cv is the molar heat capacity at constant volume and n the number of moles of the gas.

b. The change in internal energy of the gas and the work done by the gas are equal in magnitude in an adibatic process.

c. The internal energy does not change in an isothermal process.

d. No heat is added or removed in an adiabatic process.

## Wednesday, April 30, 2008

### IIT JEE Physics Model Questions 30th April

1. Identify the set which has one quantity derived from fundamental quantities involved in other quantities

a. length, velocity and mass
b. length, acceleration, and time
c. mass, time and acceleration
d. length, mass and time

2. Which of the following magnitudes represent the vectors that add to zero.

a. 2,4,8
b. 4,8,16
c. 1,2,1
d. 0.5,1,2

3. A large stone is thrown from a tower of height h with a speed of v. The stone will hit the ground with maximum speed if it is thrown

a. vertically downward
b. vertically upward
c. horizontally
d. the speed does not depend on the initial direction

4. Identify the correct statements

a. Speed is magnitude of velocity.
b. Average speed is magnitude of average velocity
c. Velocity is distance covered divided by time taken.
d. Instantaneous velocity is square root of average velocity.

5. Identify the correct statements

a. A frame of reference in which Newton’s first law is valid is called an inertial frame of reference.
b. A particle remains unaccelerated only when the vector sum of all forces acting on the particle is zero.
c. All frames moving with a constant acceleration with respect to an inertial frame are themselves inertial.
d. Inertia is a property of particles that determines the acceleration of different particle subject to the same force.

6. A body is moving on curved path. Which of the quantities given below may remain constant during the motion of the body?
a. velocity
b. speed
c. magnitude of acceleration
d. acceleration

7. Statement 1
A proton exerts attractive force on protons in the nucleus.

Statement 2

For separations less than 10-15 m, nuclear forces of attraction between particles of a nucleus are stronger than coulomb repulsion force.

a. Statement 1 is false, statement 2 is true.
b. Both statements are true, statement 2 is not a correct reason for 1.
c. Both statements are false.
d. Both statements are true, statement 2 is a correct explanation of statement 1.

8. Statement 1
The magnitude of the kinetic fiction is proportional to normal force acting between the two bodies.

Statement 2
The parallel component of contact force between two components is called friction.

a. Statement 1 is true, but statement 2 is false.
b. Statement 1 is false, but statement 2 is true.
c. Both statements are true.
d. Both statements are false.

9. Statement 1.
The equation of a wave traveling in the positive x direction with a constant speed is y = f(t-x/v)

Statement 2
The function f can be a function a function representing simple harmonic motion.

e. Statement 1 is true, but statement 2 is false.
f. Statement 1 is false, but statement 2 is true.
g. Both statements are true.
h. Both statements are false.