12583 + Mcqs in Physics Page 186 McqOptions

9251.	The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to [AIIMS 2003]
A.	h1/2
B.	h
C.	h3/2
D.	h2
Answer» B. h

Discussion

9252.	A bullet is fired from a gun. The force on the bullet is given by \[F=600-2\times {{10}^{5}}t\], where F is in newtons and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet [CBSE PMT 1998]
A.	9 Ns
B.	Zero
C.	0.9 Ns
D.	1.8 Ns
Answer» D. 1.8 Ns

Discussion

9253.	Acceleration of a particle, executing SHM, at it?s mean position is [MH CET (Med.) 2002]
A.	Infinity
B.	Varies
C.	Maximum
D.	Zero
Answer» E.

Discussion

9254.	Cathode rays are similar to visible light rays in that [SCRA 1994]
A.	They both can be deflected by electric and magnetic fields
B.	They both have a definite magnitude of wavelength
C.	They both can ionise a gas through which they pass
D.	They both can expose a photographic plate
Answer» E.

Discussion

9255.	Assertion : Only microwaves are used in radar. Reason : Because microwaves have very small wavelength.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9256.	Assertion : In Hertz experiment, the electric vector of radiation produced by the source gap is parallel to the gap. Reason : Production of sparks between the detector gap is maximum when it is placed perpendicular to the source gap.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

9257.	Assertion : The electrical conductivity of earth?s atmosphere decrease with altitude. Reason : The high energy particles (i.e. g-rays and cosmic rays) coming from outer space and entering our earth?s atmosphere causes ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

9258.	A force of 50 dynes is acted on a body of mass 5 g which is at rest for an interval of 3 seconds, then impulse is [AFMC 1998]
A.	\[0.15\times {{10}^{-3}}\,Ns\]
B.	\[0.98\times {{10}^{-3}}\,Ns\]
C.	\[1.5\times {{10}^{-3}}\,Ns\]
D.	\[2.5\times {{10}^{-3}}\,Ns\]
Answer» D. \[2.5\times {{10}^{-3}}\,Ns\]

Discussion

9259.	In an ac circuit, the r.m.s. value of current, Irms is related to the peak current, I0 by the relation [AFMC 2002]
A.	\[{{I}_{rms}}=\frac{1}{\pi }{{I}_{0}}\]
B.	\[{{I}_{rms}}=\frac{1}{\sqrt{2}}{{I}_{0}}\]
C.	\[{{I}_{rms}}=\sqrt{2}{{I}_{0}}\]
D.	\[{{I}_{rms}}=\pi {{I}_{0}}\]
Answer» C. \[{{I}_{rms}}=\sqrt{2}{{I}_{0}}\]

Discussion

9260.	Assertion : When the speed of an electron increases its specific charge decreases. Reason : Specific charge is the ratio of the charge to mass. [AIIMS 2001]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

9261.	The electron in a hydrogen atom makes a transition\[{{n}_{1}}\to {{n}_{2}}\], where \[{{n}_{1}}\] and \[{{n}_{2}}\] are the principal quantum numbers of the two states. Assume the Bohr model to be valid. The time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are [IIT 1998; KCET 2005]
A.	\[{{n}_{1}}=4,\ {{n}_{2}}=2\]
B.	\[{{n}_{1}}=8,\ {{n}_{2}}=2\]
C.	\[{{n}_{1}}=8,\ {{n}_{2}}=1\]
D.	\[{{n}_{1}}=6,\ {{n}_{2}}=3\]
Answer» E.

Discussion

9262.	Assertion : If \[\|\vec{A}+\vec{B}\|\ =\ \|\vec{A}-\vec{B}\|\], then angle between \[\vec{A}\] and \[\vec{B}\] is 90° Reason : \[\vec{A}+\vec{B}\ =\ \vec{B}+\vec{A}\]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

9263.	Assertion : The specific heat of a gas is an adiabatic process is zero and in an isothermal process is infinite. Reason : Specific heat of a gas in directly proportional to change of heat in system and inversely proportional to change in temperature.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9264.	Two planets of radii in the ratio 2 : 3 are made from the material of density in the ratio 3 : 2. Then the ratio of acceleration due to gravity \[{{g}_{1}}/{{g}_{2}}\] at the surface of the two planets will be [J & K CET 2004]
A.	1
B.	2.25
C.	4/9
D.	0.12
Answer» B. 2.25

Discussion

9265.	Minimum excitation potential of Bohr's first orbit in hydrogen atom is [BHU 1998; JIPMER 2001, 02; Pb. PMT 2004]
A.	13.6 V
B.	3.4 V
C.	10.2 V
D.	3.6 V
Answer» D. 3.6 V

Discussion

9266.	Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be [CBSE PMT 1993]
A.	3
B.	6
C.	5
D.	2
Answer» C. 5

Discussion

9267.	Assertion : Magnetic field interacts with a moving charge and not with a stationary charge. Reason : A moving charge produces a magnetic field.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9268.	Assertion : Neutral temperature of a thermocouple does not depend upon temperature of cold junction. Reason : Its value is constant for the given metals of the couple.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

9269.	Two insulated metallic spheres of \[3\mu F\] and \[5\mu F\] capacitances are charged to 300 V and 500V respectively. The energy loss, when they are connected by a wire is [CPMT 1999; KCET 2000; Pb. PMT 1999, 2001]
A.	0.012 J
B.	0.0218 J
C.	0.0375 J
D.	3.75 J
Answer» D. 3.75 J

Discussion

9270.	The ratio of minimum to maximum wavelength in Balmer series is [MP PET 2000]
A.	5 : 9
B.	5 : 36
C.	1 : 4
D.	3 : 4
Answer» B. 5 : 36

Discussion

9271.	In an A.C. circuit the current [CPMT 2005]
A.	Always leads the voltage
B.	Always lags behind the voltage
C.	Is always in phase with the voltage
D.	May lead or lag behind or be in phase with the voltage
Answer» E.

Discussion

9272.	Assertion : The reverberation time dependent on the the shape of enclosure, position of source and observer. Reason : The unit of absorption coefficient in mks system is metric sabine. [EAMCET 2004]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

9273.	A parallel plate condenser is connected with the terminals of a battery. The distance between the plates is\[6mm\]. If a glass plate (dielectric constant\[K=9\]) of \[4.5mm\] is introduced between them, then the capacity will become
A.	2 times
B.	The same
C.	3 times
D.	4 times
Answer» D. 4 times

Discussion

9274.	An observer standing near the sea shore observes 54 waves per minute. If the wavelength of the water wave is 10m then the velocity of water wave is [Kerala (Engg.) 2005]
A.	540 ms-1
B.	5.4 ms-1
C.	0.184 ms-1
D.	9 ms-1
Answer» E.

Discussion

9275.	A wave has velocity u in medium P and velocity 2u in medium Q. If the wave is incident in medium P at an angle of 30° then the angle of refraction will be [J & K CET 2005]
A.	30°
B.	45°
C.	60°
D.	90°
Answer» E.

Discussion

9276.	A point source emits sound equally in all directions in a non-absorbing medium, Two points P and Q are at distance of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is [CBSE PMT 2005]
A.	9 : 4
B.	2 : 3
C.	3 : 2
D.	4 : 9
Answer» B. 2 : 3

Discussion

9277.	What is the modulation index of an over modulated wave
A.	1
B.	Zero
C.	< 1
D.	> 1
Answer» E.

Discussion

9278.	Assertion : Average value of ac over a complete cycle is always zero. Reason : Average value of ac is always defined over half cycle.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

9279.	The three vectors \[\overrightarrow{A}=3\hat{i}-2\hat{j}+\hat{k},\,\,\overrightarrow{B}=\hat{i}-3\hat{j}+5\hat{k}\] and \[\overrightarrow{C}=2\hat{i}+\hat{j}-4\hat{k}\] form
A.	An equilateral triangle
B.	Isosceles triangle
C.	A right angled triangle
D.	No triangle
Answer» D. No triangle

Discussion

9280.	A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is [CBSE PMT 2003]
A.	B
B.	2 B
C.	4 B
D.	B/2
Answer» B. 2 B

Discussion

9281.	Assertion : An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube. Reason : Electric field require low voltage.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» E. If assertion is false but reason is true.

Discussion

9282.	Two spherical conductors A and B of radius a and b (b > a) are placed in air concentrically B is given charge + Q coulomb and A is grounded. The equivalent capacitance of these is [MP PMT 2001]
A.	\[4\pi {{\varepsilon }_{0}}\frac{ab}{b-a}\]
B.	\[4\pi {{\varepsilon }_{0}}\,(a+b)\]
C.	\[4\pi {{\varepsilon }_{0}}b\]
D.	\[4\pi {{\varepsilon }_{0}}\frac{{{b}^{2}}}{b-a}\]
Answer» E.

Discussion

9283.	Assertion : The universal gravitational constant is same as acceleration due to gravity. Reason : Gravitational constant and acceleration due to gravity have same dimensional formula.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» E. If assertion is false but reason is true.

Discussion

9284.	Assertion : In order to hit a target, a man should point his rifle in the same direction as target. Reason : The horizontal range of the bullet is dependent on the angle of projectile with horizontal direction.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

9285.	The thickness of a metallic plate is 0.4 cm. The temperature between its two surfaces is \[{{20}^{o}}C\]. The quantity of heat flowing per second is 50 calories from \[5c{{m}^{2}}\] area. In CGS system, the coefficient of thermal conductivity will be
A.	0.4
B.	0.6
C.	0.2
D.	0.5
Answer» D. 0.5

Discussion

9286.	In hydrogen atom, when electron jumps from second to first orbit, then energy emitted is [AIEEE 2002]
A.	? 13.6 eV
B.	? 27.2 eV
C.	? 6.8 eV
D.	None of these
Answer» E.

Discussion

9287.	Long distance short-wave radio broadcasting uses [AFMC 1996]
A.	Ground wave
B.	Ionospheric wave
C.	Direct wave
D.	Sky wave
Answer» D. Sky wave

Discussion

9288.	What type of modulation is employed in India for radio transmission
A.	Amplitude modulation
B.	Frequency modulation
C.	Pulse modulation
D.	None of these
Answer» B. Frequency modulation

Discussion

9289.	A liquid boils when its vapour pressure equals [MP PET 2002]
A.	The atmospheric pressure
B.	Pressure of 76.0 cm column of mercury
C.	The critical pressure
D.	The dew point of the surroundings
Answer» B. Pressure of 76.0 cm column of mercury

Discussion

9290.	At 100°C, the substance that causes the most severe burn, is [KCET 1999; UPSEAT 1999]
A.	Oil
B.	Steam
C.	Water
D.	Hot air
Answer» C. Water

Discussion

9291.	The volume of a gas is reduced adiabatically to \[\frac{1}{4}\] of its volume at 27°C, if the value of \[\gamma =1.4,\] then the new temperature will be [DPMT 2000]
A.	\[350\times {{4}^{0.4}}K\]
B.	\[300\times {{4}^{0.4}}\]K
C.	\[150\times {{4}^{0.4}}\]K
D.	None of these
Answer» C. \[150\times {{4}^{0.4}}\]K

Discussion

9292.	A current of 0.1 A circulates around a coil of 100 turns and having a radius equal to 5cm. The magnetic field set up at the centre of the coil is (m0 = 4p ´ 10?7 weber/amp-metre) [DPMT 2002]
A.	2 ´ 10?5 Tesla
B.	4 ´ 10?5 Tesla
C.	8p ´ 10?5 Tesla
D.	4p ´ 10?5 Tesla
Answer» E.

Discussion

9293.	Assertion : The setting sun appears to be red. Reason : Scattering of light is directly proportional to the wavelength. [AIIMS 2000]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

9294.	Assertion : Blue colour of sky appears due to scattering of blue colour. Reason : Blue colour has shortest wave length in visible spectrum. [AIIMS 2001]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9295.	Assertion : The refractive index of diamond is \[\sqrt{6}\] and that of liquid is \[\sqrt{3}\]. If the light travels from diamond to the liquid, it will totally reflected when the angle of incidence is 30o. Reason : \[\mu =\frac{1}{\sin C},\] where m is the refractive index of diamond with respect to liquid. [AIIMS 2000]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

9296.	Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be [MP PET 1993]
A.	Increases in the first circuit and decreases in the other
B.	Increases in both the circuits
C.	Decreases in both the circuits
D.	Decreases in the first circuit and increases in the other
Answer» E.

Discussion

9297.	Assertion : Blue star is at high temperature than red star. Reason : Wein?s displacement law states that \[T\propto (1/{{\lambda }_{m}})\]. [AIIMS 2002]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9298.	Cathode rays enter into a uniform magnetic field perpendicular to the direction of the field. In the magnetic field their path will be [MP PMT/PET 1998]
A.	Straight line
B.	Circle
C.	Parabolic
D.	Ellipse
Answer» C. Parabolic

Discussion

9299.	Assertion : When a solid iron ball is heated, percentage increase is its volume is largest. Reason : Coefficient of superficial expansion is twice that of linear expansion where as coefficient of volume expansion is three time of linear expansion.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9300.	The radius of hydrogen atom in its ground state is \[5.3\times {{10}^{-11}}m\]. After collision with an electron it is found to have a radius of \[21.2\times {{10}^{-11}}m\]. What is the principal quantum number n of the final state of the atom [CBSE PMT 1994; CPMT 2001; MH CET 2000]
A.	n = 4
B.	n = 2
C.	n = 16
D.	n = 3
Answer» C. n = 16

Discussion

Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to [AIIMS 2003]

A bullet is fired from a gun. The force on the bullet is given by \[F=600-2\times {{10}^{5}}t\], where F is in newtons and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet [CBSE PMT 1998]

Acceleration of a particle, executing SHM, at it?s mean position is [MH CET (Med.) 2002]

Cathode rays are similar to visible light rays in that [SCRA 1994]

Assertion : Only microwaves are used in radar. Reason : Because microwaves have very small wavelength.

Assertion : In Hertz experiment, the electric vector of radiation produced by the source gap is parallel to the gap. Reason : Production of sparks between the detector gap is maximum when it is placed perpendicular to the source gap.

A force of 50 dynes is acted on a body of mass 5 g which is at rest for an interval of 3 seconds, then impulse is [AFMC 1998]

In an ac circuit, the r.m.s. value of current, Irms is related to the peak current, I0 by the relation [AFMC 2002]

Assertion : When the speed of an electron increases its specific charge decreases. Reason : Specific charge is the ratio of the charge to mass. [AIIMS 2001]

Assertion : If \[|\vec{A}+\vec{B}|\ =\ |\vec{A}-\vec{B}|\], then angle between \[\vec{A}\] and \[\vec{B}\] is 90° Reason : \[\vec{A}+\vec{B}\ =\ \vec{B}+\vec{A}\]

Assertion : The specific heat of a gas is an adiabatic process is zero and in an isothermal process is infinite. Reason : Specific heat of a gas in directly proportional to change of heat in system and inversely proportional to change in temperature.

Two planets of radii in the ratio 2 : 3 are made from the material of density in the ratio 3 : 2. Then the ratio of acceleration due to gravity \[{{g}_{1}}/{{g}_{2}}\] at the surface of the two planets will be [J & K CET 2004]

Minimum excitation potential of Bohr's first orbit in hydrogen atom is [BHU 1998; JIPMER 2001, 02; Pb. PMT 2004]

Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be [CBSE PMT 1993]

Assertion : Magnetic field interacts with a moving charge and not with a stationary charge. Reason : A moving charge produces a magnetic field.

Assertion : Neutral temperature of a thermocouple does not depend upon temperature of cold junction. Reason : Its value is constant for the given metals of the couple.

Two insulated metallic spheres of \[3\mu F\] and \[5\mu F\] capacitances are charged to 300 V and 500V respectively. The energy loss, when they are connected by a wire is [CPMT 1999; KCET 2000; Pb. PMT 1999, 2001]

The ratio of minimum to maximum wavelength in Balmer series is [MP PET 2000]

In an A.C. circuit the current [CPMT 2005]

Assertion : The reverberation time dependent on the the shape of enclosure, position of source and observer. Reason : The unit of absorption coefficient in mks system is metric sabine. [EAMCET 2004]

A parallel plate condenser is connected with the terminals of a battery. The distance between the plates is\[6mm\]. If a glass plate (dielectric constant\[K=9\]) of \[4.5mm\] is introduced between them, then the capacity will become

An observer standing near the sea shore observes 54 waves per minute. If the wavelength of the water wave is 10m then the velocity of water wave is [Kerala (Engg.) 2005]

A wave has velocity u in medium P and velocity 2u in medium Q. If the wave is incident in medium P at an angle of 30° then the angle of refraction will be [J & K CET 2005]

A point source emits sound equally in all directions in a non-absorbing medium, Two points P and Q are at distance of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is [CBSE PMT 2005]

What is the modulation index of an over modulated wave

Assertion : Average value of ac over a complete cycle is always zero. Reason : Average value of ac is always defined over half cycle.

The three vectors \[\overrightarrow{A}=3\hat{i}-2\hat{j}+\hat{k},\,\,\overrightarrow{B}=\hat{i}-3\hat{j}+5\hat{k}\] and \[\overrightarrow{C}=2\hat{i}+\hat{j}-4\hat{k}\] form

A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is [CBSE PMT 2003]

Assertion : An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube. Reason : Electric field require low voltage.

Two spherical conductors A and B of radius a and b (b > a) are placed in air concentrically B is given charge + Q coulomb and A is grounded. The equivalent capacitance of these is [MP PMT 2001]

Assertion : The universal gravitational constant is same as acceleration due to gravity. Reason : Gravitational constant and acceleration due to gravity have same dimensional formula.

Assertion : In order to hit a target, a man should point his rifle in the same direction as target. Reason : The horizontal range of the bullet is dependent on the angle of projectile with horizontal direction.

The thickness of a metallic plate is 0.4 cm. The temperature between its two surfaces is \[{{20}^{o}}C\]. The quantity of heat flowing per second is 50 calories from \[5c{{m}^{2}}\] area. In CGS system, the coefficient of thermal conductivity will be

In hydrogen atom, when electron jumps from second to first orbit, then energy emitted is [AIEEE 2002]

Long distance short-wave radio broadcasting uses [AFMC 1996]

What type of modulation is employed in India for radio transmission

A liquid boils when its vapour pressure equals [MP PET 2002]

At 100°C, the substance that causes the most severe burn, is [KCET 1999; UPSEAT 1999]

The volume of a gas is reduced adiabatically to \[\frac{1}{4}\] of its volume at 27°C, if the value of \[\gamma =1.4,\] then the new temperature will be [DPMT 2000]

A current of 0.1 A circulates around a coil of 100 turns and having a radius equal to 5cm. The magnetic field set up at the centre of the coil is (m0 = 4p ´ 10?7 weber/amp-metre) [DPMT 2002]

Assertion : The setting sun appears to be red. Reason : Scattering of light is directly proportional to the wavelength. [AIIMS 2000]

Assertion : Blue colour of sky appears due to scattering of blue colour. Reason : Blue colour has shortest wave length in visible spectrum. [AIIMS 2001]

Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be [MP PET 1993]

Assertion : Blue star is at high temperature than red star. Reason : Wein?s displacement law states that \[T\propto (1/{{\lambda }_{m}})\]. [AIIMS 2002]

Cathode rays enter into a uniform magnetic field perpendicular to the direction of the field. In the magnetic field their path will be [MP PMT/PET 1998]

Assertion : When a solid iron ball is heated, percentage increase is its volume is largest. Reason : Coefficient of superficial expansion is twice that of linear expansion where as coefficient of volume expansion is three time of linear expansion.

The radius of hydrogen atom in its ground state is \[5.3\times {{10}^{-11}}m\]. After collision with an electron it is found to have a radius of \[21.2\times {{10}^{-11}}m\]. What is the principal quantum number n of the final state of the atom [CBSE PMT 1994; CPMT 2001; MH CET 2000]