Cohesive force is experienced between [MH CET 2001]

Molecules of different substances

1 a.m.u. is equivalent to [UPSEAT 2001]

\[1.5\times {{10}^{-19}}Joule\]

\[1.6\times {{10}^{-12}}Joule\]

\[1.6\times {{10}^{-19}}Joule\]

\[1.5\,\times {{10}^{-10}}Joule\]

\[1.5\times {{10}^{-19}}Joule\]

Assertion : Friction is a self-adjusting force. Reason : Friction does not depend upon mass of the body.

If assertion is false but reason is true.

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.

For a certain process the molar heat capacity of an ideal gas is found to be \[\left( {{C}_{v}}+\frac{R}{2} \right).\] For the given process it can be concluded that

\[\frac{{{V}^{2}}}{P}=\] constant

Assertion : The mirrors used in search lights are parabolic and not concave spherical. Reason : In a concave spherical mirror the image formed is always virtual.

If the assertion and reason both are false.

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.

A child with mass m is standing at the edge of a playground merry-go-round (A large uniform disc which rotates in horizontal plane about a fixed vertical axis in parks) with moment of inertia Vs I, radius R, and initial angular velocity w as shown in the figure. The child jumps off the edge of the merry-go-round with a velocity v with respect to the ground in direction tangent to periphery of the disc as shown. The new angular veloity of the merry-go-round is :

\[\sqrt{\frac{I{{\omega }^{2}}-m{{v}^{2}}}{I}}\]

\[\sqrt{\frac{(I+m{{R}^{2}}){{\omega }^{2}}-m{{v}^{2}}}{I}}\]

\[\frac{(I\omega -m{{R}^{2}})\omega -mvR}{I}\]

Assertion : Aeroplanes are made to run on the runway before take off, so that they acquire the necessary lift. Reason : According to Bernoulli's theorem, as velocity increases pressure decreases and viceversa.

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.

At a certain instant a stationary transverse wave is found to have maximum kinetic energy. The appearance of string at that instant is [AIIMS 1995]

Sinusoidal shape with amplitude A/3

Sinusoidal shape with amplitude A/2

Sinusoidal shape with amplitude A

Assertion : The minimum number of non coplanar vectors whose sum can be zero, is four. Reason : The resultant of two vectors of unequal magnitude can be zero.

If the assertion and reason both are false.

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.

Wavefront means [RPMT 1997, 98]

All particles have opposite phase of vibrations

All particles in it have same phase

All particles have opposite phase of vibrations

Few particles are in same phase, rest are in opposite phase

Assertion : Torque on the coil is the maximum, when coil is suspended in a radial magnetic field. Reason : The torque tends to rotate the coil on its own axis.

If assertion is true but reason is false.

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.

The extreme wavelengths of Paschen series are

\[0.365\mu m\]and \[0.565\mu m\]

\[0.818\mu m\]and \[1.89\mu m\]

Assertion : Power developed in circular motion is always zero. Reason : Work done in case of circular motion is zero.

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.

In a wave, the path difference corresponding to a phase difference of f is [MP PET 2000]

\[\frac{\lambda }{\pi }\varphi \]

\[\frac{\pi }{2\lambda }\varphi \]

\[\frac{\pi }{\lambda }\varphi \]

\[\frac{\lambda }{2\pi }\varphi \]

\[\frac{\lambda }{\pi }\varphi \]

What is the equivalent thermal conductivity of the rods in figure given below, if the length of each cylinder be \[\ell \] and area of cylinder having thermal conductivities\[{{\operatorname{K}}_{1}}\]and \[{{K}_{3}}\]be A while that of the middle cylinder haying thermal conductivity \[{{K}_{2}}\] be 2A?

\[\frac{1}{\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]

\[\frac{5}{2\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]

\[\frac{1}{\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]

\[\frac{2}{5\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] decrease

All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] increase

\[{{E}_{c}}\] and \[{{E}_{v}}\] increase, but \[{{E}_{g}}\] decreases

\[{{E}_{c}}\] and \[{{E}_{v}}\] decrease, but \[{{E}_{g}}\] increases

All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] decrease

Mosley's law relates the frequencies of line X-rays with the following characteristics of the target element [CPMT 1980; NCERT 1985]

Interplaner spacing of the atomic planes

Consider telecommunication through optical fibres. Which of the following statements is not true [AIEEE 2003]

Optical fibres have extremely low transmission loss

Optical fibres may have homogeneous core with a suitable cladding

Optical fibres can be of graded refractive index

Optical fibres are subject to electromagnetic interference from outside

Optical fibres have extremely low transmission loss

12583 + Mcqs in Physics in Joint Entrance Exam - Main (JEE Main) Page 8 McqOptions

351.	A ball is dropped from a height of 20 m above the surface of water in a lake. The refractive index of water is 4.3. A fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is 12.8 m above the water surface, the fish sees the speed of ball as\[[Take\text{ }g=10m/{{s}^{2}}]\]
A.	9m/s
B.	12m/s
C.	16m/s
D.	21.33 m/s
Answer» D. 21.33 m/s

Discussion

352.	The relation between the linear magnification \[m,\] the object distance \[u\] and the focal length \[f\] is
A.	\[m=\frac{f-u}{f}\]
B.	\[m=\frac{f}{f-u}\]
C.	\[m=\frac{f+u}{f}\]
D.	\[m=\frac{f}{f+u}\]
Answer» C. \[m=\frac{f+u}{f}\]

Discussion

353.	A plane progressive simple harmonic sound wave of angular frequency \[680\text{ }rad/s\] moves with speed 340 m/s in the direction which makes equal angle with each x, y and z-axis. The phase difference (\[{{\phi }_{1}}-{{\phi }_{2}}\]) between the oscillations of the particle in the medium located at the positions \[(\sqrt{3,}\sqrt{3,}\sqrt{3})\]and \[(2\sqrt{3,}\,2\sqrt{3,}\,2\sqrt{3})\] is (assume\[\cos \theta >0\])
A.	2 radian
B.	3 radian
C.	4 radian
D.	6 radian
Answer» E.

Discussion

354.	A solid that transmits light in visible region and has a very low melting point possesses [J & K CET 2001]
A.	Metallic bonding
B.	Ionic bonding
C.	Covalent bonding
D.	Vander Waal?s bonding
Answer» E.

Discussion

355.	The potential energy of a conservative system is given by\[\operatorname{U} = a{{y}^{2}}-by\], where y represents the position of the particle and a as well as b are constants. What is the force acting on the system?
A.	\[-ay\]
B.	\[-by\]
C.	\[2ay-b\]
D.	\[\operatorname{b}-2ay\]
Answer» E.

Discussion

356.	Cohesive force is experienced between [MH CET 2001]
A.	Magnetic substances
B.	Molecules of different substances
C.	Molecules of same substances
D.	None of these
Answer» D. None of these

Discussion

357.	Two slits, 4 mm apart, are illuminated by light of wavelength 6000 Å. What will be the fringe width on a screen placed 2m from the slits [MP PET 2000]
A.	0.12 mm
B.	0.3 mm
C.	3.0 mm
D.	4.0 mm
Answer» C. 3.0 mm

Discussion

358.	1 a.m.u. is equivalent to [UPSEAT 2001]
A.	\[1.6\times {{10}^{-12}}Joule\]
B.	\[1.6\times {{10}^{-19}}Joule\]
C.	\[1.5\,\times {{10}^{-10}}Joule\]
D.	\[1.5\times {{10}^{-19}}Joule\]
Answer» D. \[1.5\times {{10}^{-19}}Joule\]

Discussion

359.	The work per unit volume to stretch the length by 1% of a wire with cross sectional area of \[1\,m{{m}^{2}}\] will be. \[[Y=9\times {{10}^{11}}\,N/{{m}^{2}}]\] [RPET 1999]
A.	\[9\times {{10}^{11}}\,J\]
B.	\[4.5\times {{10}^{7}}\,J\]
C.	\[9\times {{10}^{7}}J\]
D.	\[4.5\times {{10}^{11}}\,J\]
Answer» C. \[9\times {{10}^{7}}J\]

Discussion

360.	Assertion : Friction is a self-adjusting force. Reason : Friction does not depend upon mass of the body.
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

361.	The ratio of the energy of an X-ray photon of wavelength 1 Å to that of visible light of wavelength 5000 Å is [EAMCET (Med.) 1995]
A.	1: 5000
B.	5000 : 1
C.	1 :25 \[\times \]106
D.	25 \[\times \]106
Answer» C. 1 :25 \[\times \]106

Discussion

362.	Which of the following is not a unit of time [UPSEAT 2001]
A.	Leap year
B.	Micro second
C.	Lunar month
D.	Light year
Answer» E.

Discussion

363.	From the following V-T diagram as shown in the figure. What is true about pressure?
A.	\[{{p}_{1}}<{{p}_{2}}\]
B.	\[{{p}_{1}}>{{p}_{2}}\]
C.	\[{{p}_{1}}={{p}_{2}}\]
D.	Cannot predict
Answer» B. \[{{p}_{1}}>{{p}_{2}}\]

Discussion

364.	A gas expands adiabatically at constant pressure such that its temperature \[T\,\propto \,a/\sqrt{V}.\] The value of \[\gamma =({{C}_{p}}/{{C}_{V}})\] of the gas is
A.	1.30
B.	1.5
C.	1.67
D.	2
Answer» C. 1.67

Discussion

365.	For a certain process the molar heat capacity of an ideal gas is found to be \[\left( {{C}_{v}}+\frac{R}{2} \right).\] For the given process it can be concluded that
A.	PV = constant
B.	\[\frac{P}{V}=\] constant
C.	\[\frac{{{V}^{2}}}{P}=\] constant
D.	none of these
Answer» C. \[\frac{{{V}^{2}}}{P}=\] constant

Discussion

366.	Assertion : The mirrors used in search lights are parabolic and not concave spherical. Reason : In a concave spherical mirror the image formed is always virtual.
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

367.	Four wires of identical length, diameters and of the same material are stretched on a sonometre wire. If the ratio of their tensions is 1 : 4 : 9 : 16 then the ratio of their fundamental frequencies are [KCET 2000]
A.	16 : 9 : 4 : 1
B.	4 : 3 : 2 : 1
C.	1 : 4 : 2 : 16
D.	1 : 2 : 3 : 4
Answer» E.

Discussion

368.	In a circuit, the current lags behind the voltage by a phase difference of \[\pi /2.\] The circuit contains which of the following [AIIMS 2001]
A.	Only R
B.	Only L
C.	Only C
D.	R and C
Answer» C. Only C

Discussion

369.	A child with mass m is standing at the edge of a playground merry-go-round (A large uniform disc which rotates in horizontal plane about a fixed vertical axis in parks) with moment of inertia Vs I, radius R, and initial angular velocity w as shown in the figure. The child jumps off the edge of the merry-go-round with a velocity v with respect to the ground in direction tangent to periphery of the disc as shown. The new angular veloity of the merry-go-round is :
A.	\[\sqrt{\frac{I{{\omega }^{2}}-m{{v}^{2}}}{I}}\]
B.	\[\sqrt{\frac{(I+m{{R}^{2}}){{\omega }^{2}}-m{{v}^{2}}}{I}}\]
C.	\[\frac{I\omega -mvR}{I}\]
D.	\[\frac{(I\omega -m{{R}^{2}})\omega -mvR}{I}\]
Answer» E.

Discussion

370.	Ice starts forming in a lake with water at \[0{}^\circ C\]when the atmospheric temperature is \[-10{}^\circ C\]. If the time taken for the first 1 cm of ice to be formed is 7 hours, then the time taken for the thickness of ice to change from 1 cm to 2 cm is
A.	7 hours
B.	14 hours
C.	21 hours
D.	3.5 hours
Answer» D. 3.5 hours

Discussion

371.	1 mole of a gas with \[\gamma =\text{7/5}\] is mixed with 1 mole of a gas with \[\gamma =5\text{/3,}\] then the value of \[\gamma \] for the resulting mixture is
A.	44323
B.	44318
C.	44230
D.	44389
Answer» D. 44389

Discussion

372.	In a closed vessel, pressure increases by 0.4% when temperature increases by. What is the initial temperature?
A.	250 K
B.	\[250{}^\circ C\]
C.	25 K
D.	\[25{}^\circ C\]
Answer» B. \[250{}^\circ C\]

Discussion

373.	Assertion : Aeroplanes are made to run on the runway before take off, so that they acquire the necessary lift. Reason : According to Bernoulli's theorem, as velocity increases pressure decreases and viceversa.
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

374.	At a certain instant a stationary transverse wave is found to have maximum kinetic energy. The appearance of string at that instant is [AIIMS 1995]
A.	Sinusoidal shape with amplitude A/3
B.	Sinusoidal shape with amplitude A/2
C.	Sinusoidal shape with amplitude A
D.	Straight line
Answer» E.

Discussion

375.	Transverse waves of same frequency are generated in two steel wires A and B. The diameter of A is twice of B and the tension in A is half that in B. The ratio of velocities of wave in A and B is [KCET 2001]
A.	\[1\ :\ 3\sqrt{2}\]
B.	\[1\ :\ 2\sqrt{2}\]
C.	\[1\ :\ 2\]
D.	\[\sqrt{2}\ :\ 1\]
Answer» C. \[1\ :\ 2\]

Discussion

376.	A source of sound S emitting waves of frequency 100 Hz and an observer 0 are located at some distance from each other. The source is moving with a speed of \[19.4m{{s}^{-1}}\] at an angle of \[60{}^\circ \] with the source observer line as shown in the figure. .The observer is at rest. The apparent frequency observed by the observer is (velocity of sound in air \[330m{{s}^{-1}}\])
A.	103 Hz
B.	106 Hz
C.	97 Hz
D.	100 Hz
Answer» B. 106 Hz

Discussion

377.	The sound carried by air from a sitar to a listener is a wave of the following type [MP PMT 1987; RPET 2001]
A.	Longitudinal stationary
B.	Transverse progressive
C.	Transverse stationary
D.	Longitudinal progressive
Answer» E.

Discussion

378.	For the production of X-rays of wavelength 0.1 Å the minimum potential difference will be [MP PMT 1994; RPMT 1995]
A.	12.4 kV
B.	24.8 kV
C.	124 kV
D.	248 kV
Answer» D. 248 kV

Discussion

379.	A point source of light is placed 4 m below the surface of water of refractive index 5 / 3. The minimum diameter of a disc which should be placed over the source on the surface of water to cut?off all light coming out of water is [CBSE PMT 1994; JIPMER 2001, 02]
A.	2 m
B.	6 m
C.	4 m
D.	3 m
Answer» C. 4 m

Discussion

380.	A block is given velocity 10 m/s along the fixed inclined as shown in figure from the bottom of the inclined plane. Find the total distance travelled along the inclined plane, if the coefficient of friction is equal to 0.5:
A.	5m
B.	10m
C.	\[\frac{25}{3}m\]
D.	\[\frac{50}{3}m\]
Answer» C. \[\frac{25}{3}m\]

Discussion

381.	What is the minimum stopping distance for a vehicle of mass m moving with speed v along a level road. If the coefficient of friction between the tyres and the road is \[x=40\,cm\]
A.	\[\frac{{{v}^{2}}}{2\mu g}\]
B.	\[\frac{2{{v}^{2}}}{\mu g}\]
C.	\[\frac{{{v}^{2}}}{\mu g}\]
D.	none of these
Answer» B. \[\frac{2{{v}^{2}}}{\mu g}\]

Discussion

382.	A block of mass 10 kg is kept on the fixed incline having coefficient of friction 0.8. Find the force of friction exerted on the block by inclined:
A.	100 N
B.	64 N
C.	80 N
D.	60 N
Answer» E.

Discussion

383.	Assertion : The minimum number of non coplanar vectors whose sum can be zero, is four. Reason : The resultant of two vectors of unequal magnitude can be zero.
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

384.	Two waves having intensity in the ratio 25 : 4 produce interference. The ratio of the maximum to the minimum intensity is [CPMT 1999]
A.	5 : 2
B.	7 : 3
C.	49 : 9
D.	9 : 49
Answer» D. 9 : 49

Discussion

385.	Wavefront means [RPMT 1997, 98]
A.	All particles in it have same phase
B.	All particles have opposite phase of vibrations
C.	Few particles are in same phase, rest are in opposite phase
D.	None of these
Answer» B. All particles have opposite phase of vibrations

Discussion

386.	Wave front of a wave has direction with wave motion [RPMT 1997]
A.	Parallel
B.	Perpendicular
C.	Opposite
D.	At an angle of q
Answer» C. Opposite

Discussion

387.	The temperature of a substance increases by 27°C. On the Kelvin scale this increase is equal to [CPMT 1993]
A.	300 K
B.	2.46 K
C.	27 K
D.	7 K
Answer» D. 7 K

Discussion

388.	Assertion : Torque on the coil is the maximum, when coil is suspended in a radial magnetic field. Reason : The torque tends to rotate the coil on its own axis.
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

389.	The velocity of an electron in the second orbit of sodium atom (atomic number = 11) is v. The velocity of an electron in its fifth orbit will be
A.	v
B.	\[\frac{22}{5}v\]
C.	\[\frac{5}{2}v\]
D.	\[\frac{2}{5}v\]
Answer» E.

Discussion

390.	The extreme wavelengths of Paschen series are
A.	\[0.365\mu m\]and \[0.565\mu m\]
B.	\[0.818\mu m\]and \[1.89\mu m\]
C.	\[1.45\mu m\]and \[4.04\mu m\]
D.	\[2.27\mu m\]and \[7.43\mu m\]
Answer» C. \[1.45\mu m\]and \[4.04\mu m\]

Discussion

391.	X-rays can be used to study crystal structure, if the wavelength lies in the range
A.	2 Å to 0.1 Å
B.	10 Å to 5 Å
C.	50 Å to 10 Å
D.	100 Å to 50 Å
Answer» B. 10 Å to 5 Å

Discussion

392.	Assertion : Power developed in circular motion is always zero. Reason : Work done in case of circular motion is zero.
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

393.	Which of the following is a unit of energy [AFMC 2002]
A.	Unit
B.	Watt
C.	Horse Power
D.	None
Answer» E.

Discussion

394.	In a wave, the path difference corresponding to a phase difference of f is [MP PET 2000]
A.	\[\frac{\pi }{2\lambda }\varphi \]
B.	\[\frac{\pi }{\lambda }\varphi \]
C.	\[\frac{\lambda }{2\pi }\varphi \]
D.	\[\frac{\lambda }{\pi }\varphi \]
Answer» D. \[\frac{\lambda }{\pi }\varphi \]

Discussion

395.	What is the equivalent thermal conductivity of the rods in figure given below, if the length of each cylinder be \[\ell \] and area of cylinder having thermal conductivities\[{{\operatorname{K}}_{1}}\]and \[{{K}_{3}}\]be A while that of the middle cylinder haying thermal conductivity \[{{K}_{2}}\] be 2A?
A.	\[\frac{5}{2\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]
B.	\[\frac{1}{\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]
C.	\[\frac{2}{5\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]
D.	None of these
Answer» B. \[\frac{1}{\left[ \frac{1}{{{K}_{1}}}+\frac{1}{2{{K}_{2}}}+\frac{1}{{{K}_{3}}} \right]}\]

Discussion

396.	A hemispherical glass body of radius 10 cm and refractive index 1.5 is silvered on its curved surface. A small air bubble is 6 cm below the flat surface inside it along the axis. The position of the image of the air bubble made by the mirror is seen:
A.	14 cm below flat surface
B.	20 cm below flat surface
C.	16 cm below flat surface
D.	30 cm below flat surface
Answer» C. 16 cm below flat surface

Discussion

397.	If the lattice constant of this semiconductor is decreased, then which of the following is correct?
A.	All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] increase
B.	\[{{E}_{c}}\] and \[{{E}_{v}}\] increase, but \[{{E}_{g}}\] decreases
C.	\[{{E}_{c}}\] and \[{{E}_{v}}\] decrease, but \[{{E}_{g}}\] increases
D.	All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] decrease
Answer» D. All \[{{E}_{c}},{{E}_{g}},{{E}_{v}}\] decrease

Discussion

398.	A string of length 2 m is fixed at both ends. If this string vibrates in its fourth normal mode with a frequency of 500 Hz then the waves would travel on its with a velocity of [BCECE 2005]
A.	125 m/s
B.	250 m/s
C.	500 m/s
D.	1000 m/s
Answer» D. 1000 m/s

Discussion

399.	Mosley's law relates the frequencies of line X-rays with the following characteristics of the target element [CPMT 1980; NCERT 1985]
A.	Its density
B.	Its atomic weight
C.	Its atomic number
D.	Interplaner spacing of the atomic planes
Answer» D. Interplaner spacing of the atomic planes

Discussion

400.	Consider telecommunication through optical fibres. Which of the following statements is not true [AIEEE 2003]
A.	Optical fibres may have homogeneous core with a suitable cladding
B.	Optical fibres can be of graded refractive index
C.	Optical fibres are subject to electromagnetic interference from outside
D.	Optical fibres have extremely low transmission loss
Answer» D. Optical fibres have extremely low transmission loss

Discussion

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

The relation between the linear magnification \[m,\] the object distance \[u\] and the focal length \[f\] is

A solid that transmits light in visible region and has a very low melting point possesses [J & K CET 2001]

The potential energy of a conservative system is given by\[\operatorname{U} = a{{y}^{2}}-by\], where y represents the position of the particle and a as well as b are constants. What is the force acting on the system?

Cohesive force is experienced between [MH CET 2001]

Two slits, 4 mm apart, are illuminated by light of wavelength 6000 Å. What will be the fringe width on a screen placed 2m from the slits [MP PET 2000]

1 a.m.u. is equivalent to [UPSEAT 2001]

The work per unit volume to stretch the length by 1% of a wire with cross sectional area of \[1\,m{{m}^{2}}\] will be. \[[Y=9\times {{10}^{11}}\,N/{{m}^{2}}]\] [RPET 1999]

Assertion : Friction is a self-adjusting force. Reason : Friction does not depend upon mass of the body.

The ratio of the energy of an X-ray photon of wavelength 1 Å to that of visible light of wavelength 5000 Å is [EAMCET (Med.) 1995]

Which of the following is not a unit of time [UPSEAT 2001]

From the following V-T diagram as shown in the figure. What is true about pressure?

A gas expands adiabatically at constant pressure such that its temperature \[T\,\propto \,a/\sqrt{V}.\] The value of \[\gamma =({{C}_{p}}/{{C}_{V}})\] of the gas is

For a certain process the molar heat capacity of an ideal gas is found to be \[\left( {{C}_{v}}+\frac{R}{2} \right).\] For the given process it can be concluded that

Assertion : The mirrors used in search lights are parabolic and not concave spherical. Reason : In a concave spherical mirror the image formed is always virtual.

Four wires of identical length, diameters and of the same material are stretched on a sonometre wire. If the ratio of their tensions is 1 : 4 : 9 : 16 then the ratio of their fundamental frequencies are [KCET 2000]

In a circuit, the current lags behind the voltage by a phase difference of \[\pi /2.\] The circuit contains which of the following [AIIMS 2001]

Ice starts forming in a lake with water at \[0{}^\circ C\]when the atmospheric temperature is \[-10{}^\circ C\]. If the time taken for the first 1 cm of ice to be formed is 7 hours, then the time taken for the thickness of ice to change from 1 cm to 2 cm is

1 mole of a gas with \[\gamma =\text{7/5}\] is mixed with 1 mole of a gas with \[\gamma =5\text{/3,}\] then the value of \[\gamma \] for the resulting mixture is

In a closed vessel, pressure increases by 0.4% when temperature increases by. What is the initial temperature?

Assertion : Aeroplanes are made to run on the runway before take off, so that they acquire the necessary lift. Reason : According to Bernoulli's theorem, as velocity increases pressure decreases and viceversa.

At a certain instant a stationary transverse wave is found to have maximum kinetic energy. The appearance of string at that instant is [AIIMS 1995]

Transverse waves of same frequency are generated in two steel wires A and B. The diameter of A is twice of B and the tension in A is half that in B. The ratio of velocities of wave in A and B is [KCET 2001]

The sound carried by air from a sitar to a listener is a wave of the following type [MP PMT 1987; RPET 2001]

For the production of X-rays of wavelength 0.1 Å the minimum potential difference will be [MP PMT 1994; RPMT 1995]

A point source of light is placed 4 m below the surface of water of refractive index 5 / 3. The minimum diameter of a disc which should be placed over the source on the surface of water to cut?off all light coming out of water is [CBSE PMT 1994; JIPMER 2001, 02]

A block is given velocity 10 m/s along the fixed inclined as shown in figure from the bottom of the inclined plane. Find the total distance travelled along the inclined plane, if the coefficient of friction is equal to 0.5:

What is the minimum stopping distance for a vehicle of mass m moving with speed v along a level road. If the coefficient of friction between the tyres and the road is \[x=40\,cm\]

A block of mass 10 kg is kept on the fixed incline having coefficient of friction 0.8. Find the force of friction exerted on the block by inclined:

Assertion : The minimum number of non coplanar vectors whose sum can be zero, is four. Reason : The resultant of two vectors of unequal magnitude can be zero.

Two waves having intensity in the ratio 25 : 4 produce interference. The ratio of the maximum to the minimum intensity is [CPMT 1999]

Wavefront means [RPMT 1997, 98]

Wave front of a wave has direction with wave motion [RPMT 1997]

The temperature of a substance increases by 27°C. On the Kelvin scale this increase is equal to [CPMT 1993]

Assertion : Torque on the coil is the maximum, when coil is suspended in a radial magnetic field. Reason : The torque tends to rotate the coil on its own axis.

The velocity of an electron in the second orbit of sodium atom (atomic number = 11) is v. The velocity of an electron in its fifth orbit will be

The extreme wavelengths of Paschen series are

X-rays can be used to study crystal structure, if the wavelength lies in the range

Assertion : Power developed in circular motion is always zero. Reason : Work done in case of circular motion is zero.

Which of the following is a unit of energy [AFMC 2002]

In a wave, the path difference corresponding to a phase difference of f is [MP PET 2000]

A hemispherical glass body of radius 10 cm and refractive index 1.5 is silvered on its curved surface. A small air bubble is 6 cm below the flat surface inside it along the axis. The position of the image of the air bubble made by the mirror is seen:

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

A string of length 2 m is fixed at both ends. If this string vibrates in its fourth normal mode with a frequency of 500 Hz then the waves would travel on its with a velocity of [BCECE 2005]

Mosley's law relates the frequencies of line X-rays with the following characteristics of the target element [CPMT 1980; NCERT 1985]

Consider telecommunication through optical fibres. Which of the following statements is not true [AIEEE 2003]