60 objective type questions on Physics subject for Kerala Engineering Architecture Medical (KEAM) Engineering Entrance Exam

**Ques:** The radioactive nucleus _{7}N^{13} decays to _{6}C^{13} through the emission of

(a) Neutron

(b) Proton

(c) Electron

(d) Positron

Ans. (d)

**Ques. **A current of 16A flows through molten NaCl for 10 minutes. The amount of metallic sodium that appears at the negative would be

(a) 11.5 gm

(b) 2.3 gm

(c) 1.15 gm

(d) 0.23 gm

Ans. (b)

**Ques. **A convex lens when placed in the first position forms a real image of an object on a fixed screen. The distance between the object and the screen is 75 cm. On displacing the lens from first position by 25 cm to the second position, again a real image is formed on the screen. Then the focal length of the lens is

(a) 25.0 cm

(b) 16.7 cm

(c) 50.3 cm

(d) 33.3 cm

Ans. (b)

**Ques.** A particle moving in one dimension with a constant acceleration of 2 m/s^{2} is observed to cover a distance of 5 m during a particular interval of one second. The distance covered by particle in the next one second interval is (in metres)

(a) 12

(b) 6

(c) 7

(d) 10

Ans. (c)

**Ques. **Find the angle of a prism of dispersive power 0.021 and refractive index 1.53 from an achromatic combination with prism of angle 4.2° and dispersive power 0.045 having refractive index 1.65. Find the resultant deviation.

(a) 5°

(b) 1°

(c) 2°

(d) 3.12°

Ans. (d)

**Ques. **A radioactive sample consists of two distinct species having equal number of atoms initially. The mean life of one species is t and that of the other is 5t. The decay products in both cases are stable. A plot is made of the total number of radioactive nuclei as a function of time. Which of the following figure best represent the form of this plot :

Ans. (d)

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**Ques. **Two lenses, each of power has P = +5 are taken dioptres. What distance should be kept between them so that their resultant power obtained is negative

(a) More than 40 cm

(b) Equal to 40 cm

(c) Equal to 0.10 cm

(d) Less than 10 cm

Ans. (a)

**Ques.** The mean free path of conduction electron in copper is about 4 x 10^{-8} m. Find the electric field which can give an average, 2 eV energy to a conduction electron in a block of copper

(a) 5 x 10^{7} V/m

(b) 6 x 10^{7} V/m

(c) 7 x 10^{7} V/m

(d) 8 x 10^{7} V/m

Ans. (a)

**Ques. **The amplitude of a plane progressive wave of frequency 1000 Hz propagating in air is 0.2 x 10^{7} m. The amplitude of particle velocity will be

(a) 1.26 x 10^{–4} m/s

(b) 0.73 x 10^{–4} m/s

(c) 2.1 x 10^{–4} m/s

(d) 1.80 x 10^{–4} m/s

Ans. (a)

**Ques. **If a sound-source and a listener are moving in the same direction with the same velocity then the ratio of the actual frequency of sound and the apparent frequency heard by the listener will be

(a) 1:2

(b) 1:1

(c) 2:1

(d) 1:4

Ans. (b)

**Ques. **Which statement is false?

(a) The RMS velocity of the gas molecules is proportional to its absolute temperature

(b) The RMS velocity of the gas molecules is inversely proportional to the square root of the molecular weight

(c) The gas pressure per unit volume is 2/3 of the mean kinetic energy

(d) In a perfect gas, there is no force of attraction among the molecules

Ans. (a)

**Ques. **In the forward bias on *P-N* junction is increased from zero to 0.05V, then no current in the circuit flows. The contact potential of junction plane is

(a) Zero

(b) 0.05V

(c) More than 0.05V

(d) Less than 0.05V

Ans. (b)

**Ques. **The half life of a radioactive material is 34.65 seconds. If at any time 10^{22} atoms are active, then the activity of that material is

(a) 1 x 10^{20} disintegration/s

(b) 2 x 10^{20} disintegration/s

(c) 3 x 10^{20} disintegration/s

(d) 4 x 10^{20} disintegration/s

Ans. (b)

**Ques. **The wave number of first line of Balmer series in hydrogen atom is 1.52 x 10^{6} m^{–1}. The wave number of first line of Lyman series in Be^{3+} will be

(a) 2.43 x 10^{8} m^{–1}

(b) 1.31 x 10^{8} m^{–1
}(c) 5.44 x 10^{8} m^{–1}

(d) 6.83 x 10^{8} m^{–1}

Ans. (b)

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**Ques. **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) Deuterium atom

(c) Single ionized helium

(d) Double ionized lithium

Ans. (d)

**Ques. **An electric field along +*X* direction and a magnetic field are applied on an electron moving along +*Z* direction. What should be the direction of magnetic field so that the motion of the electron remains unaffected

(a) +*X* direction

(b) +*Y *direction

(c) –*X* direction

(d) –*Y* direction

Ans. (b)

**Ques. **If two conducting spheres are separately charged and then brought in contact

(a) The total energy of the two spheres is conserved

(b) The total charge on the two spheres is conserved

(c) Both the total energy and charge are conserved

(d) The final potential is always the mean of the original potentials of the two spheres

Ans. (b)

**Ques. **A liquid is flowing in a horizontal uniform capillary tube under a constant pressure difference *P*. The value of pressure for which the rate of flow of the liquid is doubled when the radius and length both are doubled is

(a) *P*

(b) 3P/4

(c) P/2

(d) P/4

Ans. (d)

**Ques.** A light bulb is placed between two plane mirrors inclined at an angle of 60^{o}. The number of images formed are

(a) 6

(b) 2

(c) 5

(d) 4

Ans. (c)

**Ques.** The period of a satellite in a circular orbit of radius *R* is *T*. What is the period of another satellite in a circular orbit of radius 4*R*?

(a) 4*T*

(b) T/8

(c) T/4

(d) 8*T
*Ans. (d)

**Ques. **The light reflected by a plane mirror may form a real image

(a) If the rays incident on the mirror are diverging

(b) If the rays incident on the mirror are converging

(c) If the object is placed very close to the mirror

(d) Under no circumstances

Ans. (b)

**Ques. **A ball is dropped from a bridge 125m above a river. 2s later a second ball is thrown straight down. What must be the initial velocity of second ball so that hit the water surface simultaneously

(a) 26.66 m/s

(b) 66.26 m/s

(c) 43.5 m/s

(d) 5 m/s

Ans. (a)

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**Ques. **At sun rise or sunset, the sun looks more red than at mid-day because

(a) The sun is hottest at these times

(b) Of the scattering of light

(c) Of the effects of refraction

(d) Of the effects of diffraction

Ans. (b)

**Ques. **In a *PN* junction photo cell, the value of photo-electromotive force produced by monochromatic light is proportional to

(a) The voltage applied at the *PN* junction

(b) The barrier voltage at the *PN* junction

(c) The intensity of the light falling on the cell

(d) The frequency of the light falling on the cell

Ans. (c)

**Ques. **In an electron gun the control grid is given a negative potential relative to cathode in order to

(a) Decelerate electrons

(b) Repel electrons and thus to control the number of electrons passing through it

(c) To select electrons of same velocity and to converge them along the axis

(d) To decrease the kinetic energy of electrons

Ans. (b)

**Ques. **The work functions for sodium and copper are 2eV and 4eV. Which of them is suitable for a photocell with 4000 Å light

(a) Copper

(b) Sodium

(c) Both

(d) Neither of them

Ans. (b)

**Ques.** The qualities best suited for a cooking utensil are

(a) high specific heat and low thermal conductivity

(b) low specific heat and low thermal conductivity

(c) high specific heat and high thermal conductivity

(d) low specific heat and high thermal conductivity

**Ans.** (d)

**Ques.** A man runs towards mirror at a speed of 15 m /s. What is the speed of his image

(a) 7.5 m/s

(b) 15 m/s

(c) 30 m/s

(d) 45 m/s

Ans. (b)

**Ques. **The emf in a thermoelectric circuit with one junction at 0° and the other at t° C is given by E = at + bt^{2}. The neutral temperature is

(a) 2b/a

(b) a/b

(c) – a/b

(d) – a/2b

Ans. (d)

**Ques. **The half-life period of a radioactive element *x* is same as the mean life time of another radioactive element *y*. Initially both of them have the same number of atoms. Then :

(a) *x* and *y* have the same decay rate initially

(b) *x* and *y* decay at the same rate always

(c) *y* will decay at a faster rate than *x*

(d) *x* will decay at faster rate than *y
*Ans. (c)

**Ques. **In a telescope, *f*_{o} and *f*_{e} are the focal lengths of objective and eye-piece lenses respectively. In an astronomical telescope with normal adjustment, the distance between the objective and eye-piece is

(a) *f*_{o}

(b) *f*_{e}

(c) *f*_{o} + *f*_{e}

(d) *f*_{o} – *f*_{e}

Ans. (c)

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**Ques. **In Young’s double slit experiment, if one of the slits is closed then what change in the pattern is observed

(a) Interference pattern will be obtained instead of diffraction pattern

(b) Diffraction pattern will be obtained instead of interference pattern

(c) Uniform illumination will be obtained

(d) Alternate bright and dark interference rings will be obtained

Ans. (c)

**Ques.** A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of the motion of the ball is

(a) 1 : 2 : 3

(b) 1 : 4 : 9

(c) 1 : 3 : 5

(d) 1 : 5 : 3

**Ans.** (c)

**Ques. **The width of a slit is 0.3 mm. Its Fraunhofer diffraction pattern is obtained at the focal plane of a convex lens of focal length 1 m. If third minimum is formed at a distance of 5 mm from central maximum, then the wavelength of light used, is

(a) 7000Å

(b) 6500Å

(c) 6000Å

(d) 5000Å

Ans. (d)

**Ques. **The specific heat of a gas at constant volume is 21.2 J/mole/ ^{o}C. If the temperature is increased by 1°C keeping the volume constant, the change in its internal energy will be

(a) 0

(b) 21.2 J

(c) 42.2 J

(d) 10.6 J

Ans. (b)

**Ques.** Which of the following is a wrong statement?

(a) D = 1/f where f is the focal length and *D *is called the refractive power of a lens.

(b) Power is expressed in a diopter when f is in metres

(c) Power is expressed in diopter and does not depend on the system of unit used to measure f

(d) *D *is positive for convergent lens and negative for divergent lens

**Ans.** (c)

**Ques. **Two stationary sirens each producing sound of frequency 330 Hz are separated by 1km. If an observer is moving from one siren to another siren with a velocity of 2 m/s, then the number of beats heard by the observer will be-(velocity of sound is 330 m/s)

(a) 4

(b) 5

(c) 3

(d) 2

Ans. (a)

**Ques. **Holes in a semi-conductor behave as they have

(a) Negative charge

(b) Positive charge

(c) No charge

(d) Initially positive and finally negative

Ans. (b)

**Ques.** The principle of optical fibre is

(a) Diffraction

(b) Polarisation

(c) Interference

(d) Total Internal reflection

**Ans.** (d)

**Ques. **The correct statement out of the following is

(a) Intrinsic semi-conductors behave like insulators at absolute zero temperature

(b) Extrinsic semi-conductors are conductors at absolute zero temperature

(c) All metals are insulators at absolute zero temperature

(d) None of the above

Ans. (a)

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**Ques. **Two tuning forks A and B produce 6 beats/sec. The fork A is in unision with a closed pipe of length 15cm and fork B is in unision with open pipe of length 30.5 cm. The frequencies of these forks are respectively

(a) 366 Hz and 372 Hz

(b) 366 Hz and 360 Hz

(c) 360 Hz and 354 Hz

(d) 354 Hz and 348 Hz

Ans. (b)

**Ques. **A coil of self inductance 50 henry is joined to the terminals of a battery of e.m.f. 2 volts through a resistance of 10 ohm and a steady current is flowing through the circuit. If the battery is now disconnected the time in which the current will decay to 1/e of its steady value is

(a) 500 seconds

(b) 50 seconds

(c) 5 seconds

(d) 0.5 seconds

Ans. (c)

**Ques. **The scientist who experimentally showed that the electric charge is quantised only in terms of integral multiples of electronic charge is

(a) Max Born

(b) Max Planck

(c) Thomson

(d) Millikan

Ans. (d)

**Ques. **A 5 cm x 12 cm coil with number of turns 600 is placed in a magnetic field of strength 0.10 Tesla. The maximum magnetic torque acting on it when a current of 10^{–5} A is passed through it, will be

(a) 3.6 x 10^{–6} *N-*m

(b) 3.6 x 10^{–6} Dyne-cm

(c) 3.6 x 10^{6}* N-*m

(d) 3.6 x 10^{6} Dyne-m

Ans. (a)

**Ques.** The typical ionization energy of a donor in silicon is

(a) 0.1 Ev

(b) 2.0 eV

(c) 0.001 eV

(d) 10 eV

Ans. (b)

**Ques. **Infinite charges are lying at x = 1, 2, 4, 8, … meter on *X-*axis and the value of each charge is *q*. The value of intensity of electric field at point x = 0 due to these charge will be

(a) 12 x 10^{9} q N/C

(b) Zero

(c) 6 x 10^{9} q N/C

(d) 4 x 10^{9} q N/C

Ans. (a)

**Ques. **Two capillaries of same diameter are dipped into liquids of specific gravity 0.4 and 0.8 respectively. If their surface tensions are in the ratio 6 : 5 then the ratio of heights of liquids in them will be

(a) 12 : 5

(b) 5 : 12

(c) 5 : 6

(d) 8 : 4

Ans. (a)

**Ques.** A compound microscope has magnifying power as 32 and magnifying power of eye-piece is 4; then the magnifying power of the objective is

(a) 8

(b) 10

(c) 6

(d) 12

**Ans.** (a)

**Ques. **A polariser is used to

(a) Reduce intensity of light

(b) Produce polarised light

(c) Increase intensity of light

(d) Produce unpolarised light

Ans. (b)

**Ques. **Total internal reflection of light is possible when light enters from

(a) Air to glass

(b) Vacuum to air

(c) Air to water

(d) Water to air

Ans. (d)

**Ques. **The refractive indices of violet and red light are 1.54 and 1.52 respectively. If the angle of prism is 10°, then the angular dispersion is

(a) 0.02

(b) 0.2

(c) 3.06

(d) 30.6

Ans. (b)

**Ques. **If the forward voltage in a semiconductor diode is doubled, the width of the depletion layer will

(a) Become half

(b) Become one-fourth

(c) Remain unchanged

(d) Become double

Ans. (a)

**Ques.** A very broad elevator is going up vertically with a constant acceleration of 2 m/s^{2}. At the instant when its velocity is 4 m/s a ball is projected from the floor of the lift with a speed of 4m/s relative to the floor at an elevation of 30^{0}. The time taken by the ball to return the floor is:

(a) ¼ sec

(b) 1/3 sec

(c) ½ sec

(d) 1 sec

Ans. (b)

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**Ques. **As the intensity of incident light increases

(a) Photoelectric current increases

(b) Photoelectric current decreases

(c) Kinetic energy of emitted photoelectrons increases

(d) Kinetic energy of emitted photoelectrons decreases

Ans. (a)

**Ques.** If an observer is walking away from the plane mirror with 6m / sec. Then the velocity of the image with respect to observer will be

(a) 6m/sec

(b) –6m/sec

(c) 12m/sec

(d) 3m/sec

Ans. (c)

**Ques. **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

Ans. (c)

**Ques.** If one junction of thermocouple is kept at 0°C, and its e.m.f. is given by *e* = *at* + *bt*^{2}, then the neutral temperature will be :

(a) *a*/*b*

(b) –*a*/*b*

(c) *a*/2*b*

(d) –*a*/2*b
*

**Ans.**(d)

**Ques. **There are two points A and B on the extended axis of a 2 cm bar magnet. Their distances from the centre of the magnet are x and 2x respectively. The ratio of magnetic fields at points A and B will be (approximately)

(a) 8:1

(b) 4:1

(c) 4:1

(d) 8:1

Ans. (a)

**Ques. **Shown in the figure here is a convergent lens placed inside a cell filled with a liquid. The lens has focal length +20 cm when in air and its material has refractive index 1.50. If the liquid has refractive index 1.60, the focal length of the system is

(a) +80 cm

(b) –80 cm

(c) –24 cm

(d) –100 cm

Ans. (d)

**Ques. **A simple microscope has a focal length of 5 cm. The magnification at the least distance of distinct vision is

(a) 2

(b) 5

(c) 4

(d) 6

Ans. (d)

**Ques.** Ampere-hour is the unit of :

(a) quantity of charge

(b) potential

(c) energy

(d) current

**Ans.** (a)

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