X-rays and gamma rays are both electromagnetic waves. Which of the following statements is true [NCERT 1973]

X-rays have smaller wavelength than that of gamma rays

In general X-rays have larger wavelength than of gamma rays

X-rays have smaller wavelength than that of gamma rays

Gamma rays have smaller frequency than that of X-rays

Wavelength and frequency of X-rays are both larger than that of gamma rays

Bohr's atom model assumes [KCET 2005]

The nucleus is of infinite mass and is at rest

Electrons in a quantized orbit will not radiate energy

Mass of electron remains constant

Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively. Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively. For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface. [Take \[\sigma \times \,4\pi {{R}^{2}}\,\times \,{{300}^{4}}=\,\beta J{{s}^{-1}}\]] Consider two cases, first one in which A is a perfect black body and the second in which A is a non-black body. In both the cases, temperature of body A is same equal to 300K and H is at temperature 600K. For H, \[t=0\] and \[a\ne 1\]. For this situation, mark out the correct statement.

From this information we can calculate exact rate of heat loss by A in different cases.

The bodies lose their distinctiveness inside the enclosure and both of them emit the same radiation as that of the black body.

The rate of heat loss by A in both cases is the same and is equal to\[\beta \,J{{s}^{-1}}\].

The rates of heat loss by A in both the cases are different.

From this information we can calculate exact rate of heat loss by A in different cases.

Choose the correct statement [DCE 2004]

When we cool a semiconductor to 0 K then it becomes super conductor

When we heat a semiconductor its resistance increases

When we heat a semiconductor its resistance decreases

When we cool a semiconductor to 0 K then it becomes super conductor

Resistance of a semiconductor is independent of temperature

A box has been placed on train moving uniformly with speed \[{{V}_{0}}.\] The box contains ideal gas. The value of root mean square speed with respect to an observer present in the trains is \[{{V}_{1}}.\] What will be the value of root mean square speed with respect to an observer standing on the platform?

\[{{\{V_{1}^{2}+V_{0}^{2}\}}^{1/2}}\]

K is the force constant of a spring. The work done in increasing its extension from \[{{l}_{1}}\] to \[{{l}_{2}}\] will be [MP PET 1995; MP PMT 1996]

\[\frac{K}{2}({{l}_{2}}+{{l}_{1}})\]

\[\frac{K}{2}(l_{2}^{2}-l_{1}^{2})\]

In a PN-junction diode not connected to any circuit [IIT-JEE 1998]

There is an electric field at the junction directed from the P-type side to the N-type side

The potential is the same everywhere

The P-type is a higher potential than the N-type side

There is an electric field at the junction directed from the N- type side to the P- type side

There is an electric field at the junction directed from the P-type side to the N-type side

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?

The number of free conduction electrons is significant in C but small in \[Si\] and \[Ge\].

The number of free electrons for conduction is significant only in \[Si\] and \[Ge\] but small in C.

The number of free conduction electrons is significant in C but small in \[Si\] and \[Ge\].

The number of free conduction electrons is negligibly small in all the three.

The number of free electrons for conduction is significant in all the three.

An aluminum rod (Young's modulus \[=7\times {{10}^{9}}\,N/{{m}^{2}})\] has a breaking strain of 0.2%. The minimum cross-sectional area of the rod in order to support a load of \[{{10}^{4}}\]Newton's is [MP PMT 1991]

\[1\times {{10}^{-2}}\,{{m}^{2}}\]

\[1.4\times {{10}^{-3}}\,{{m}^{2}}\]

\[3.5\times {{10}^{-3}}\,{{m}^{2}}\]

\[7.1\times {{10}^{-4}}\,{{m}^{2}}\]

On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam :

goes horizontally without any deflection

The force constants of two springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. Both are stretched till their elastic energies are equal. If the stretching forces are \[{{F}_{1}}\] and \[{{F}_{2}}\], then \[{{F}_{1}}:{{F}_{2}}\] is [MP PET 2002]

\[\sqrt{{{K}_{1}}}:\sqrt{{{K}_{2}}}\]

Assertion : Two bodies at different temperatures, if brought in thermal contact do not necessary settle to the mean temperature. Reason : The two bodies may have different thermal capacities.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

When p-n junction diode is forward biased then

the depletion region is widened and barrier height is reduced

both the depletion region and barrier height are reduced

the depletion region is widened and barrier height is reduced

the depletion region is reduced and barrier height is increased

Both the depletion region and barrier height are increased

Which of the following statements is not true? In the case of a simple pendulum for small amplitudes the period of oscillation is [NCERT 1982]

Dependent on the mass, size and material of the bob

Directly proportional to square root of the length of the pendulum

Inversely proportional to the square root of the acceleration due to gravity

Dependent on the mass, size and material of the bob

A simple pendulum is set up in a trolley which moves to the right with an acceleration a on a horizontal plane. Then the thread of the pendulum in the mean position makes an angle \[\theta \] with the vertical [CPMT 1983]

\[{{\tan }^{-1}}\frac{g}{a}\] in the backward direction

\[{{\tan }^{-1}}\frac{a}{g}\] in the forward direction

\[{{\tan }^{-1}}\frac{a}{g}\] in the backward direction

\[{{\tan }^{-1}}\frac{g}{a}\] in the backward direction

\[{{\tan }^{-1}}\frac{g}{a}\] in the forward direction

Which of the following circular rods, (given radius r and length /) each made of the same material and whose ends are maintained at the same temperature will conduct most heat?

\[\operatorname{r}={{r}_{0}};1=2{{1}_{0}}\]

\[\operatorname{r}=2{{r}_{0}};l=2{{l}_{0}}\]

\[\operatorname{r}=2{{r}_{0}};l={{l}_{0}}\]

\[\operatorname{r}={{r}_{0}};1=2{{1}_{0}}\]

\[\operatorname{r}={{r}_{0}};1={{1}_{0}}\]

The wave length of light in visible part \[({{\lambda }_{V}})\] and for sound \[({{\lambda }_{S}})\] are related as [RPMT 1999]

\[{{\lambda }_{S}}={{\lambda }_{V}}\]

\[{{\lambda }_{V}}>{{\lambda }_{S}}\]

\[{{\lambda }_{S}}>{{\lambda }_{V}}\]

\[{{\lambda }_{S}}={{\lambda }_{V}}\]

12583 + Mcqs in Physics in Joint Entrance Exam - Main (JEE Main) Page 3 McqOptions

101.	If vm is the velocity of sound in moist air, vd is the velocity of sound in dry air, under identical conditions of pressure and temperature [KCET 2002, 03]
A.	vm > vd
B.	vm < vd
C.	vm = vd
D.	vmvd = 1
Answer» B. vm < vd

Discussion

102.	Two springs have spring constants \[{{K}_{A}}\] and \[{{K}_{B}}\] and \[{{K}_{A}}>{{K}_{B}}\]. The work required to stretch them by same extension will be [RPMT 1999]
A.	More in spring A
B.	More in spring B
C.	Equal in both
D.	Noting can be said
Answer» B. More in spring B

Discussion

103.	The bulk modulus of a liquid of density 8000 kg\[8000kg\,{{m}^{-3}}\]is \[2\times {{10}^{9}}N\,{{m}^{-2}}\]. The speed of sound in that liquid is (\[in\,m\,{{s}^{-1}}\])
A.	200
B.	250
C.	100
D.	500
Answer» E.

Discussion

104.	A water fall is 84 metres high. If half of the potential energy of the falling water gets converted to heat, the rise in temperature of water will be [JIPMER 2002]
A.	0.098°C
B.	0.98°C
C.	9.8°C
D.	0.0098°C
Answer» B. 0.98°C

Discussion

105.	X-rays and gamma rays are both electromagnetic waves. Which of the following statements is true [NCERT 1973]
A.	In general X-rays have larger wavelength than of gamma rays
B.	X-rays have smaller wavelength than that of gamma rays
C.	Gamma rays have smaller frequency than that of X-rays
D.	Wavelength and frequency of X-rays are both larger than that of gamma rays
Answer» B. X-rays have smaller wavelength than that of gamma rays

Discussion

106.	Bohr's atom model assumes [KCET 2005]
A.	The nucleus is of infinite mass and is at rest
B.	Electrons in a quantized orbit will not radiate energy
C.	Mass of electron remains constant
D.	All the above conditions
Answer» E.

Discussion

107.	How many wavelength of \[K{{r}^{86}}\] are there in one metre [MNR 1985; UPSEAT 2000; Pb. PET 2004]
A.	1553164.13
B.	1650763.73
C.	652189.63
D.	2348123.73
Answer» C. 652189.63

Discussion

108.	In P-type semiconductor, there is [MP PMT 1989]
A.	An excess of one electron
B.	Absence of one electron
C.	A missing atom
D.	A donar level
Answer» C. A missing atom

Discussion

109.	In the above ques., the height to which the lift takes the passenger is
A.	3.6 meters
B.	8 meters
C.	1.8 meters
D.	36 meters
Answer» E.

Discussion

110.	If \[{{I}_{0}}\] is me intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled?
A.	\[4{{I}_{0}}\]
B.	\[2{{I}_{0}}\]
C.	\[\frac{{{I}_{0}}}{2}\]
D.	\[{{I}_{0}}\]
Answer» B. \[2{{I}_{0}}\]

Discussion

111.	Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively. Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively. For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface. [Take \[\sigma \times \,4\pi {{R}^{2}}\,\times \,{{300}^{4}}=\,\beta J{{s}^{-1}}\]] Consider two cases, first one in which A is a perfect black body and the second in which A is a non-black body. In both the cases, temperature of body A is same equal to 300K and H is at temperature 600K. For H, \[t=0\] and \[a\ne 1\]. For this situation, mark out the correct statement.
A.	The bodies lose their distinctiveness inside the enclosure and both of them emit the same radiation as that of the black body.
B.	The rate of heat loss by A in both cases is the same and is equal to\[\beta \,J{{s}^{-1}}\].
C.	The rates of heat loss by A in both the cases are different.
D.	From this information we can calculate exact rate of heat loss by A in different cases.
Answer» D. From this information we can calculate exact rate of heat loss by A in different cases.

Discussion

112.	A particle executing simple harmonic motion with amplitude of 0.1 m. At a certain instant when its displacement is 0.02 m, its acceleration is 0.5 m/s2. The maximum velocity of the particle is (in m/s) [MP PET 2003]
A.	0.01
B.	0.05
C.	0.5
D.	0.25
Answer» D. 0.25

Discussion

113.	Joule-second is the unit of [CPMT 1990; CBSE PMT 1993; BVP 2003]
A.	Work
B.	Momentum
C.	Pressure
D.	Angular momentum
Answer» E.

Discussion

114.	An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n = 3 state, how much energy is required to ionize it [MP PMT 1995]
A.	13.6 eV
B.	4.53 eV
C.	3.4 eV
D.	1.51 eV
Answer» E.

Discussion

115.	Choose the correct statement [DCE 2004]
A.	When we heat a semiconductor its resistance increases
B.	When we heat a semiconductor its resistance decreases
C.	When we cool a semiconductor to 0 K then it becomes super conductor
D.	Resistance of a semiconductor is independent of temperature
Answer» C. When we cool a semiconductor to 0 K then it becomes super conductor

Discussion

116.	The frequency of a sound wave is n and its velocity is v. If the frequency is increased to \[4n,\] the velocity of the wave will be [MP PET 2000]
A.	v
B.	\[2v\]
C.	\[4v\]
D.	\[v/4\]
Answer» B. \[2v\]

Discussion

117.	A box has been placed on train moving uniformly with speed \[{{V}_{0}}.\] The box contains ideal gas. The value of root mean square speed with respect to an observer present in the trains is \[{{V}_{1}}.\] What will be the value of root mean square speed with respect to an observer standing on the platform?
A.	\[{{V}_{1}}+{{V}_{0}}\]
B.	\[{{V}_{1}}\]
C.	\[{{\{V_{1}^{2}+V_{0}^{2}\}}^{1/2}}\]
D.	None
Answer» D. None

Discussion

118.	K is the force constant of a spring. The work done in increasing its extension from \[{{l}_{1}}\] to \[{{l}_{2}}\] will be [MP PET 1995; MP PMT 1996]
A.	\[K({{l}_{2}}-{{l}_{1}})\]
B.	\[\frac{K}{2}({{l}_{2}}+{{l}_{1}})\]
C.	\[K(l_{2}^{2}-l_{1}^{2})\]
D.	\[\frac{K}{2}(l_{2}^{2}-l_{1}^{2})\]
Answer» E.

Discussion

119.	A narrow electron beam passes undeviated through an electric field \[E=3\times {{10}^{4}}volt/m\]and an overlapping magnetic field \[B=2\times {{10}^{-3}}Weber/{{m}^{2}}\]. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is [MP PET 1995]
A.	60 m/s
B.	\[10.3\times {{10}^{7}}m/s\]
C.	\[1.5\times {{10}^{7}}m/s\]
D.	\[0.67\times {{10}^{-7}}m/s\]
Answer» D. \[0.67\times {{10}^{-7}}m/s\]

Discussion

120.	The process of adding impurities to the pure semiconductor is called [MH CET 2002]
A.	Drouping
B.	Drooping
C.	Doping
D.	None of these
Answer» D. None of these

Discussion

121.	In a PN-junction diode not connected to any circuit [IIT-JEE 1998]
A.	The potential is the same everywhere
B.	The P-type is a higher potential than the N-type side
C.	There is an electric field at the junction directed from the N- type side to the P- type side
D.	There is an electric field at the junction directed from the P-type side to the N-type side
Answer» D. There is an electric field at the junction directed from the P-type side to the N-type side

Discussion

122.	If a ladder weighing 250 N is placed against a smooth vertical wall having coefficient of friction between it and floor is 0.3, then what is the maximum force of friction available at the point of contact between the ladder and the floor [BHU 2004]
A.	75 N
B.	50 N
C.	35 N
D.	25 N
Answer» B. 50 N

Discussion

123.	Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?
A.	The number of free electrons for conduction is significant only in \[Si\] and \[Ge\] but small in C.
B.	The number of free conduction electrons is significant in C but small in \[Si\] and \[Ge\].
C.	The number of free conduction electrons is negligibly small in all the three.
D.	The number of free electrons for conduction is significant in all the three.
Answer» B. The number of free conduction electrons is significant in C but small in \[Si\] and \[Ge\].

Discussion

124.	In Milikan's oil drop experiment, a charged drop falls with terminal velocity V. If an electric field E is applied in vertically upward direction then it starts moving in upward direction with terminal velocity 2V. If magnitude of electric field is decreased to \[\frac{E}{2}\], then terminal velocity will become [CBSE PMT 1999]
A.	\[\frac{V}{2}\]
B.	V
C.	\[\frac{3V}{2}\]
D.	2V
Answer» D. 2V

Discussion

125.	An aluminum rod (Young's modulus \[=7\times {{10}^{9}}\,N/{{m}^{2}})\] has a breaking strain of 0.2%. The minimum cross-sectional area of the rod in order to support a load of \[{{10}^{4}}\]Newton's is [MP PMT 1991]
A.	\[1\times {{10}^{-2}}\,{{m}^{2}}\]
B.	\[1.4\times {{10}^{-3}}\,{{m}^{2}}\]
C.	\[3.5\times {{10}^{-3}}\,{{m}^{2}}\]
D.	\[7.1\times {{10}^{-4}}\,{{m}^{2}}\]
Answer» E.

Discussion

126.	On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam :
A.	bends downwards
B.	bends upwards
C.	becomes narrower
D.	goes horizontally without any deflection
Answer» C. becomes narrower

Discussion

127.	Consider the YDSE arrangement shown in figure. If \[d=10\lambda \] then position of \[{{8}^{th}}\] maxima is
A.	\[y=\frac{D}{10}\]
B.	\[y=\frac{D}{3}\]
C.	\[y=\frac{4}{5}D\]
D.	\[y=\frac{4D}{3}\]
Answer» E.

Discussion

128.	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

129.	The force constants of two springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. Both are stretched till their elastic energies are equal. If the stretching forces are \[{{F}_{1}}\] and \[{{F}_{2}}\], then \[{{F}_{1}}:{{F}_{2}}\] is [MP PET 2002]
A.	\[{{K}_{1}}:{{K}_{2}}\]
B.	\[{{K}_{2}}:{{K}_{1}}\]
C.	\[\sqrt{{{K}_{1}}}:\sqrt{{{K}_{2}}}\]
D.	\[K_{1}^{2}:K_{2}^{2}\]
Answer» D. \[K_{1}^{2}:K_{2}^{2}\]

Discussion

130.	A mass m is vertically suspended from a spring of negligible mass; the system oscillates with a frequency n. What will be the frequency of the system if a mass 4 m is suspended from the same spring [CBSE PMT 1998]
A.	\[n/4\]
B.	\[4n\]
C.	\[n/2\]
D.	\[2n\]
Answer» D. \[2n\]

Discussion

131.	If the period of oscillation of mass m suspended from a spring is 2 sec, then the period of mass 4m will be [AIIMS 1998]
A.	1 sec
B.	2 sec
C.	3 sec
D.	4 sec
Answer» E.

Discussion

132.	Assertion : Two bodies at different temperatures, if brought in thermal contact do not necessary settle to the mean temperature. Reason : The two bodies may have different thermal capacities.
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

133.	The PN junction diode is used as [CPMT 1972; AFMC 1997; CBSE PMT 1999; AIIMS 1999; RPMT 2000; MP PMT 04]
A.	An amplifier
B.	A rectifier
C.	An oscillator
D.	A modulator
Answer» C. An oscillator

Discussion

134.	When p-n junction diode is forward biased then
A.	both the depletion region and barrier height are reduced
B.	the depletion region is widened and barrier height is reduced
C.	the depletion region is reduced and barrier height is increased
D.	Both the depletion region and barrier height are increased
Answer» B. the depletion region is widened and barrier height is reduced

Discussion

135.	At what altitude in metre will the acceleration due to gravity be 25% of that at the earth's surface (Radius of earth = R metre) [ISM Dhanbad 1994]
A.	\[\frac{1}{4}R\]
B.	R
C.	\[\frac{3}{8}R\]
D.	\[\frac{R}{2}\]
Answer» C. \[\frac{3}{8}R\]

Discussion

136.	At what height from the ground will the value of ?g? be the same as that in 10 km deep mine below the surface of earth [RPET 1999]
A.	20 km
B.	10 km
C.	15 km
D.	5 km
Answer» B. 10 km

Discussion

137.	Rutherford?s a-particle experiment showed that the atoms have [AFMC 2001]
A.	Proton
B.	Nucleus
C.	Neutron
D.	Electrons
Answer» C. Neutron

Discussion

138.	Which of the following statements is not true? In the case of a simple pendulum for small amplitudes the period of oscillation is [NCERT 1982]
A.	Directly proportional to square root of the length of the pendulum
B.	Inversely proportional to the square root of the acceleration due to gravity
C.	Dependent on the mass, size and material of the bob
D.	Independent of the amplitude
Answer» C. Dependent on the mass, size and material of the bob

Discussion

139.	An electron changes its position from orbit \[n=4\] to the orbit \[n=2\] of an atom. The wavelength of the emitted radiation?s is (R = Rydberg?s constant) [BHU 2004]
A.	\[\frac{16}{R}\]
B.	\[\frac{16}{3R}\]
C.	\[\frac{16}{5R}\]
D.	\[\frac{16}{7R}\]
Answer» C. \[\frac{16}{5R}\]

Discussion

140.	The mass and diameter of a planet are twice those of earth. The period of oscillation of pendulum on this planet will be (If it is a second's pendulum on earth) [IIT 1973; DCE 2002]
A.	\[\frac{1}{\sqrt{2}}\] sec
B.	\[2\sqrt{2}\]sec
C.	2 sec
D.	\[\frac{1}{2}\]sec
Answer» C. 2 sec

Discussion

141.	A simple pendulum is set up in a trolley which moves to the right with an acceleration a on a horizontal plane. Then the thread of the pendulum in the mean position makes an angle \[\theta \] with the vertical [CPMT 1983]
A.	\[{{\tan }^{-1}}\frac{a}{g}\] in the forward direction
B.	\[{{\tan }^{-1}}\frac{a}{g}\] in the backward direction
C.	\[{{\tan }^{-1}}\frac{g}{a}\] in the backward direction
D.	\[{{\tan }^{-1}}\frac{g}{a}\] in the forward direction
Answer» C. \[{{\tan }^{-1}}\frac{g}{a}\] in the backward direction

Discussion

142.	Which of the following circular rods, (given radius r and length /) each made of the same material and whose ends are maintained at the same temperature will conduct most heat?
A.	\[\operatorname{r}=2{{r}_{0}};l=2{{l}_{0}}\]
B.	\[\operatorname{r}=2{{r}_{0}};l={{l}_{0}}\]
C.	\[\operatorname{r}={{r}_{0}};1=2{{1}_{0}}\]
D.	\[\operatorname{r}={{r}_{0}};1={{1}_{0}}\]
Answer» C. \[\operatorname{r}={{r}_{0}};1=2{{1}_{0}}\]

Discussion

143.	In which frequency range, space waves are normally propagated [EAMCET 2002]
A.	HF
B.	VHF
C.	UHF
D.	SHF
Answer» D. SHF

Discussion

144.	For a triode, at \[{{V}_{g}}=-1\] volt, the following observations were taken \[{{V}_{p}}=75V,\,{{I}_{p}}=2mA\], \[{{V}_{p}}=100V,\,{{I}_{p}}=4mA\]. The value of plate resistance will be [MP PMT 1989]
A.	25 kW
B.	20.8 kW
C.	12.5 kW
D.	100 kW
Answer» D. 100 kW

Discussion

145.	The wave length of light in visible part \[({{\lambda }_{V}})\] and for sound \[({{\lambda }_{S}})\] are related as [RPMT 1999]
A.	\[{{\lambda }_{V}}>{{\lambda }_{S}}\]
B.	\[{{\lambda }_{S}}>{{\lambda }_{V}}\]
C.	\[{{\lambda }_{S}}={{\lambda }_{V}}\]
D.	None of these
Answer» C. \[{{\lambda }_{S}}={{\lambda }_{V}}\]

Discussion

146.	Current gain of a transistor in common base mode is\[0.95\]. Its value in common emitter mode is
A.	\[0.95\]
B.	\[1.5\]
C.	\[19\]
D.	\[{{(19)}^{-1}}\]
Answer» D. \[{{(19)}^{-1}}\]

Discussion

147.	The number of waves contained in unit length of the medium is called [AIIMS 1998]
A.	Elastic wave
B.	Wave number
C.	Wave pulse
D.	Electromagnetic wave
Answer» C. Wave pulse

Discussion

148.	A physical quantity is measured and its value is found to be \[nu\] where \[n=\] numerical value and \[u=\] unit. Then which of the following relations is true [RPET 2003]
A.	\[n\propto {{u}^{2}}\]
B.	\[n\propto u\]
C.	\[n\propto \sqrt{u}\]
D.	\[n\propto \frac{1}{u}\]
Answer» E.

Discussion

149.	A particle executs SHM with time period 8 s. Initially, it is at its mean position. The ratio of distance travelled by it in the 1st second to that in the 2nd second is
A.	\[\sqrt{2}:1\]
B.	\[1:(\sqrt{2}-1)\]
C.	\[(\sqrt{2}+1):\sqrt{2}\]
D.	\[(\sqrt{2}-1):1\]
Answer» C. \[(\sqrt{2}+1):\sqrt{2}\]

Discussion

150.	A steel scale is calibrated for\[\text{27}{{\,}^{\text{o}}}\text{C}\text{.}\] The error in a reading of 50 cm at\[30{{\,}^{\text{o}}}\text{C}\]is \[[{{\alpha }_{steel}}=1.2\,\times \,{{10}^{-5}}/{{\,}^{o}}C]\]
A.	0.018 mm
B.	0.18 mm
C.	0.0018 mm
D.	0.16 mm
Answer» B. 0.18 mm

Discussion

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

If vm is the velocity of sound in moist air, vd is the velocity of sound in dry air, under identical conditions of pressure and temperature [KCET 2002, 03]

Two springs have spring constants \[{{K}_{A}}\] and \[{{K}_{B}}\] and \[{{K}_{A}}>{{K}_{B}}\]. The work required to stretch them by same extension will be [RPMT 1999]

The bulk modulus of a liquid of density 8000 kg\[8000kg\,{{m}^{-3}}\]is \[2\times {{10}^{9}}N\,{{m}^{-2}}\]. The speed of sound in that liquid is (\[in\,m\,{{s}^{-1}}\])

A water fall is 84 metres high. If half of the potential energy of the falling water gets converted to heat, the rise in temperature of water will be [JIPMER 2002]

X-rays and gamma rays are both electromagnetic waves. Which of the following statements is true [NCERT 1973]

Bohr's atom model assumes [KCET 2005]

How many wavelength of \[K{{r}^{86}}\] are there in one metre [MNR 1985; UPSEAT 2000; Pb. PET 2004]

In P-type semiconductor, there is [MP PMT 1989]

In the above ques., the height to which the lift takes the passenger is

If \[{{I}_{0}}\] is me intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled?

A particle executing simple harmonic motion with amplitude of 0.1 m. At a certain instant when its displacement is 0.02 m, its acceleration is 0.5 m/s2. The maximum velocity of the particle is (in m/s) [MP PET 2003]

Joule-second is the unit of [CPMT 1990; CBSE PMT 1993; BVP 2003]

An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n = 3 state, how much energy is required to ionize it [MP PMT 1995]

Choose the correct statement [DCE 2004]

The frequency of a sound wave is n and its velocity is v. If the frequency is increased to \[4n,\] the velocity of the wave will be [MP PET 2000]

K is the force constant of a spring. The work done in increasing its extension from \[{{l}_{1}}\] to \[{{l}_{2}}\] will be [MP PET 1995; MP PMT 1996]

A narrow electron beam passes undeviated through an electric field \[E=3\times {{10}^{4}}volt/m\]and an overlapping magnetic field \[B=2\times {{10}^{-3}}Weber/{{m}^{2}}\]. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is [MP PET 1995]

The process of adding impurities to the pure semiconductor is called [MH CET 2002]

In a PN-junction diode not connected to any circuit [IIT-JEE 1998]

If a ladder weighing 250 N is placed against a smooth vertical wall having coefficient of friction between it and floor is 0.3, then what is the maximum force of friction available at the point of contact between the ladder and the floor [BHU 2004]

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?

An aluminum rod (Young's modulus \[=7\times {{10}^{9}}\,N/{{m}^{2}})\] has a breaking strain of 0.2%. The minimum cross-sectional area of the rod in order to support a load of \[{{10}^{4}}\]Newton's is [MP PMT 1991]

On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam :

Consider the YDSE arrangement shown in figure. If \[d=10\lambda \] then position of \[{{8}^{th}}\] maxima is

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]

The force constants of two springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. Both are stretched till their elastic energies are equal. If the stretching forces are \[{{F}_{1}}\] and \[{{F}_{2}}\], then \[{{F}_{1}}:{{F}_{2}}\] is [MP PET 2002]

A mass m is vertically suspended from a spring of negligible mass; the system oscillates with a frequency n. What will be the frequency of the system if a mass 4 m is suspended from the same spring [CBSE PMT 1998]

If the period of oscillation of mass m suspended from a spring is 2 sec, then the period of mass 4m will be [AIIMS 1998]

Assertion : Two bodies at different temperatures, if brought in thermal contact do not necessary settle to the mean temperature. Reason : The two bodies may have different thermal capacities.

The PN junction diode is used as [CPMT 1972; AFMC 1997; CBSE PMT 1999; AIIMS 1999; RPMT 2000; MP PMT 04]

When p-n junction diode is forward biased then

At what altitude in metre will the acceleration due to gravity be 25% of that at the earth's surface (Radius of earth = R metre) [ISM Dhanbad 1994]

At what height from the ground will the value of ?g? be the same as that in 10 km deep mine below the surface of earth [RPET 1999]

Rutherford?s a-particle experiment showed that the atoms have [AFMC 2001]

Which of the following statements is not true? In the case of a simple pendulum for small amplitudes the period of oscillation is [NCERT 1982]

An electron changes its position from orbit \[n=4\] to the orbit \[n=2\] of an atom. The wavelength of the emitted radiation?s is (R = Rydberg?s constant) [BHU 2004]

The mass and diameter of a planet are twice those of earth. The period of oscillation of pendulum on this planet will be (If it is a second's pendulum on earth) [IIT 1973; DCE 2002]

A simple pendulum is set up in a trolley which moves to the right with an acceleration a on a horizontal plane. Then the thread of the pendulum in the mean position makes an angle \[\theta \] with the vertical [CPMT 1983]

Which of the following circular rods, (given radius r and length /) each made of the same material and whose ends are maintained at the same temperature will conduct most heat?

In which frequency range, space waves are normally propagated [EAMCET 2002]

For a triode, at \[{{V}_{g}}=-1\] volt, the following observations were taken \[{{V}_{p}}=75V,\,{{I}_{p}}=2mA\], \[{{V}_{p}}=100V,\,{{I}_{p}}=4mA\]. The value of plate resistance will be [MP PMT 1989]

The wave length of light in visible part \[({{\lambda }_{V}})\] and for sound \[({{\lambda }_{S}})\] are related as [RPMT 1999]

Current gain of a transistor in common base mode is\[0.95\]. Its value in common emitter mode is

The number of waves contained in unit length of the medium is called [AIIMS 1998]

A physical quantity is measured and its value is found to be \[nu\] where \[n=\] numerical value and \[u=\] unit. Then which of the following relations is true [RPET 2003]

A particle executs SHM with time period 8 s. Initially, it is at its mean position. The ratio of distance travelled by it in the 1st second to that in the 2nd second is

A steel scale is calibrated for\[\text{27}{{\,}^{\text{o}}}\text{C}\text{.}\] The error in a reading of 50 cm at\[30{{\,}^{\text{o}}}\text{C}\]is \[[{{\alpha }_{steel}}=1.2\,\times \,{{10}^{-5}}/{{\,}^{o}}C]\]