# OJEE Physics exam papers with answers

Odisha Joint Entrance Exam physics question bank includes 30 multiple choice questions with answers given at the end of each question.

Ques: The decay constant of a radioactive element is 0.01 per second. Its half life period is
(a) 693 sec
(b) 6.93 sec
(c) 0.693 sec
(d) 69.3 sec

Ans. (d)

Ques. The temperature, at which a ferromagnetic material gets converted into paramagnetic one, is known as
(a) Curic temperature
(b) Boyle temperature
(c) Critical temperature
(d) Neutral temperature

Ans. (a)

(a) Irreversible process
(b) Self disintegration process
(c) Spontaneous process
(d) All of the above

Ans. (d)

Ques. The power of an achromatic convergent lens of two lenses is + 2D. The power of convex lens is + 5D. The ratio of dispersive power of convex and concave lens will be
(a) 5 : 3
(b) 3 : 5
(c) 2 : 5
(d) 5 : 2

Ans. (b)

Ques. The potential of earth may be presumed to be zero because
(a) The earth is a huge conductor
(b) Earth revolves round the sun
(c) There is no charge in the earth
(d) The capacity of earth is zero

Ans. (a)

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Ques. When white light passes through a glass prism, one gets spectrum on the other side of the prism. In the emergent beam, the ray which is deviating least is or Deviation by a prism is lowest for
(a) Violet ray
(b) Green ray
(c) Red ray
(d) Yellow ray

Ans. (c)

Ques. The dielectric constant for pure water is
(a) 300
(b) 5
(c) 80
(d) 1

Ans. (c)

Ques. According to Bohrâ€™s theory of hydrogen atom, the angular momentum of an electron in any orbit of hydrogen atom is
(a) Directly proportional to the radius of the orbit
(b) Inversely proportional to the radius of the orbit
(c) Directly proportional to the square of the radius of the orbit
(d) Directly proportional to the square root of the radius of the orbit

Ans. (d)

Ques. A person cannot see an object lying beyond 80 cm whereas a normal person can easily see the object distant 160 cm. The focal length and the nature of the lens used to rectify this defect will be
(a) â€“ 160 cm concave
(b) â€“ 160 cm convex
(c) 60 cm concave
(d) 160 cm convex

Ans. (a)

Ques. The ratio of maximum and minimum intensities of light in a interference pattern is 9 : 1. The ratio of intensities of interfering waves will be
(a) 1 : 4
(b) 4 : 1
(c) 9 : 1
(d) 1 : 9

Ans. (b)

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Ques. The impurity atom added to germanium to make it N-type semiconductor is
(a) Arsenic
(b) Iridium
(c) Aluminium
(d) Iodine

Ans. (a)

Ques. A car is moving with a uniform speed of 72 km/h and blowing its horn of frequency 280 Hz. Another car is moving on another road, perpendicular to first road with a uniform speed of 36 km/h. If the speed of sound in air is 340 m/s and both the cars are approaching a crossing, the frequency of the sound observed by the driver of second car at the instant when the line joining the two makes an angle of 45o with the road, is
(a) 286 Hz
(b) 292 Hz
(c) 298 Hz
(d) 304 Hz

Ans. (c)

Ques. The characteristic X-ray radiation is emitted, when
(a) The electrons are accelerated to a fixed energy
(b) The source of electrons emits a monoenergetic beam
(c) The bombarding electrons knock out electrons fromÂ  the inner shell of the target atoms and one of the outer electrons falls into this vacancy
(d) The valence electrons in the target atoms are removed as a result of the collision

Ans. (c)

Ques. The length of the compound microscope is 14 cm. The magnifying power for relaxed eye is 25. If the focal length of eye lens is 5 cm, then the object distance for objective lens will be
(a) 1.8 cm
(b) 1.5 cm
(c) 2.1 cm
(d) 2.4 cm

Ans. (a)

Ques. A parallel combination of silver and copper voltameters is connected to a battery of 6V. In half an hour 1g copper and 2g silver get deposited. The electrochemical equivalents of copper and silver are 3.294 x 10â€“4 and 1.118 x 10â€“3 g/C respectively. The total current drawn from the battery is
(a) 1.72A
(b) 1.99A
(c) 2.12A
(d) 2.68A

Ans. (d)

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Ques. The root mean square velocity of gas molecules at 0Â°C will be if at N.T.P. its density is 1.43 x Kg/m3
(a) 461 m/s
(b) 164 m/s
(c) 461 cm/s
(d) 164 cm/s

Ans. (a)

Ques. By leaving the door of a small standard domestic refrigerator open it is not possible to cool a room, because it violates the
(a) First law of thermodynamics
(b) Second law of thermodynamics
(c) Law of conservation of momentum
(d) Law of conservation of energy.

Ans. (a)

Ques. The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature
(a) Decreases exponentially with increasing band gap
(b) Increases exponentially with increasing band gap
(c) Decreases with increasing temperature
(d) Is independent of the temperature and the band gap

Ans. (a)

Ques. The twisting couple per unit twist for a solid cylinder of radius 3 cm is 0.1 Newton-meter. The twisting couple per unit twist, for a hollow cylinder of same material with outer and inner radii 5 cm and 4 cm respectively, will be
(a) 0.1 Newton-meter
(b) 0.455 Newton-meter
(c) 0.91 Newton-meter
(d) 1.82 Newton-meter

Ans. (b)

Ques. In order to make the effective acceleration due to gravity equal to zero at the equator, the angular velocity of rotation of the earth about its axis should be (g = 10 msâ€“2 and radius of earth is 6400 kms)

Ans. (b)

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Ques. Which of the following is used to produce radio waves of constant amplitude?
(a) Oscillator
(b) FET
(c) Rectifier
(d) Amplifier

Ans. (a)

Ques. A condenser is charged to a potential difference of 200 Volt as a result of which it gains charge of 0.1 coulomb. When it is discharged then the energy released will be
(a) 2 Joule
(b) 10 Joule
(c) 1 Joule
(d) 20 Joule

Ans. (b)

Ques. A drop of water of volume 0.05 cm3 is pressed between two glass plates, as a consequence of which it spreads and occupies an area of 40 cm2. If theÂ  surface tension of water is 70 dyne / cm, then the normal force required to separate out the two glass plates will be in Newton
(a) 90
(b) 45
(c) 22.5
(d) 450

Ans. (b)

Ques. What should be the angle between two plane mirrors so that whatever be the angle of incidence, the incident ray and the reflected ray from the two mirrors be parallel to each other
(a) 60o
(b) 90o
(c) 120o
(d) 175o

Ans. (b)

Ques. If the focal lengths of objective and eye lens of a microscope are 1.2 cm and 3 cm respectively and the object is put 1.25 cm away from the objective lens and the final image is formed at infinity, then magnifying power of the microscope is
(a) 150
(b) 200
(c) 250
(d) 400

Ans. (b)

Ques. A tank 5 m high is half filled with water and then is filled to the top with oil of density 0.85 g/cm3. The pressure at the bottom of the tank, due to these liquids is
(a) 1.85 g/cm2
(b) 89.25 g/cm2
(c) 462.5 g/cm2
(d) 500 g/cm2

Ans. (c)

Ques. The idea of the quantum nature of light has emerged in an attempt to explain
(a) Interference
(b) Diffraction
(c) Radiation spectrum of a black body
(d) Polarisation

Ans. (c)

Ques. A convex mirror has a focal length f. A real object is placed at a distance f in front of it from the pole produces an image at
(a) Infinity
(b) f
(c) f/2
(d) 2f

Ans. (c)

Ques. Which radiation in sunlight, causes heating effect?
(a) Ultraviolet
(b) Infrared
(c) Visible light
(d) All of these

Ans. (b)

Ques. The number of wavelengths in the visible spectrum
(a) 4000
(b) 6000
(c) 2000
(d) Infinite

Ans. (d)

Ques. The radius of curvature for a convex lens is 40 cm, for each surface. Its refractive index is 1.5. The focal length will be
(a) 40 cm
(b) 20 cm
(c) 80 cm
(d) 30 cm

Ans. (a)

Ques. The centre of the diffraction pattern formed by a circular disc is always
(a) Bright
(b) Dark
(c) Sometimes bright and sometimes dark depending on distance of screen
(d) Sometimes bright and sometimes dark depending upon the size of the disc

Ans. (a)

Ques. An oxide coated filament is useful in vacuum tubes because essentially
(a) It has high melting point
(b) It can withstand high temperatures
(c) It has good machanical strength
(d) It can emit electrons at relatively lower temperatures

Ans. (d)

Ques. The focal length of the objective and the eyepiece of a microscope are 4 mm and 25 mm respectively. If the final image is formed at infinity and the length of the tube is 16 cm the magnifying power of the microscope will be
(a) â€“ 327. 5
(b) â€“ 32.57
(c) 3.275
(d) 32.75

Ans. (a)

Ques. A gas is filled in a container at pressure Po. If the mass of molecules is halved and their speeds are doubled then the resultant pressure will be
(a) Po
(b) 4Po
(c) 2Po
(d) Po/2

Ans. (b)

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Ques. An ammeter is connected in series with a silver voltameter for calibration. By passing a certain amount of current for 30 minutes the mass of silver deposited is 1.0062 g and ammeter reading is 0.52A. The error in ammeter reading is
(a) +0.02A
(b) +0.04A
(c) â€“0.02A
(d) â€“0.04A

Ans. (a)

Ques. An object is placed at a distance of 50 cm from a convex mirror. A plane mirror is placed in front of the convex mirror in such a way that it convers half of the convex mirror. If the distance between object and plane mirror is 30 cm then there is no parallax between the image formed by two mirrors, the radius of curvature of convex mirror will be
(a) 50 cm
(b) 25 cm
(c) 12.5 cm
(d) 100 cm

Ans. (b)

Ques. The difference of two liquid levels in a manometer is 10 cm and its density is 0.8 gm/cm3. If the density of air is 1.3 x 103 gm/cm3 then the velocity of air will be
(a) 347
(b) 34.7
(c) 3470
(d) 0.347

Ans. (a)

Ques. In biprism experiment the light source is
(a) Extended
(b) Narrow
(c) Multichromatic
(d) All of above

Ans. (b)

Ques. Photo cell is a device to
(a) Store photons
(b) Measure light intensity
(c) Convert photon energy into mechanical energy
(d) Store electrical energy for replacing storage batteries

Ans. (b)

Ques. The dispersive power of crown and flint glasses are 0.03 and 0.05 respectively. The refractive indices for yellow light for these glasses are 1.517 and 1.621 respectively. It is desired to form an achromatic combination of prisms of crown and flint glasses which can produced a deviation of 1Â° in the yellow ray. Find the refracting angles of the two prisms needed.
(a) 4.8Â°, 4Â°
(b) 4.8Â°, 2.4Â°
(c) 1Â°, 2.4Â°
(d) 2Â°, 3Â°

Ans. (b)