12583 + Mcqs in Physics Page 15 McqOptions

701.	A string of 7 m length has a mass of 0.035 kg. If tension in the string is 60.5 N, then speed of a wave on the string is [CBSE PMT 2001]
A.	77 m/s
B.	102 m/s
C.	110 m/s
D.	165 m/s
Answer» D. 165 m/s

Discussion

702.	In order to double the frequency of the fundamental note emitted by a stretched string, the length is reduced to \[\frac{3}{4}\]th of the original length and the tension is changed. The factor by which the tension is to be changed, is [EAMCET 2001]
A.	\[\frac{3}{8}\]
B.	\[\frac{2}{3}\]
C.	\[\frac{8}{9}\]
D.	\[\frac{9}{4}\]
Answer» E.

Discussion

703.	Two perfectly identical wires are in unison. When the tension in one wire is increased by 1%, then on sounding them together 3 beats are heard in 2 sec. The initial frequency of each wire is : [Pb. PET 2002]
A.	\[220{{s}^{-1}}\]
B.	\[320{{s}^{-1}}\]
C.	\[150{{s}^{-1}}\]
D.	\[300{{s}^{-1}}\]
Answer» E.

Discussion

704.	The first overtone of a stretched wire of given length is 320 Hz. The first harmonic is : [DPMT 2004]
A.	320 Hz
B.	160 Hz
C.	480 Hz
D.	640 Hz
Answer» C. 480 Hz

Discussion

705.	A tuning fork of frequency 392 Hz, resonates with 50 cm length of a string under tension (T). If length of the string is decreased by 2%, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is [BHU 2004]
A.	4
B.	6
C.	8
D.	12
Answer» D. 12

Discussion

706.	If \[\lambda \]=10Å, then it corresponds to [DCE 2000]
A.	Infra-red
B.	Microwave
C.	Ultra-violet
D.	X-rays
Answer» E.

Discussion

707.	In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is [AFMC 1998; CPMT 2000; Pb. PET 2002]
A.	4 : 5
B.	5 : 4
C.	5 : 9
D.	9 : 5
Answer» B. 5 : 4

Discussion

708.	Assertion : Separation of isotope is possible because of the difference in electron numbers of isotope. Reason : Isotope of an element can be separated by using a mass spectrometer. [AIIMS 1999]
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

709.	Assertion : The velocity of sound increases with increase in humidity. Reason : Velocity of sound does not depend upon the medium.
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

710.	If wavelength of a wave is \[\lambda =6000{AA}.\] Then wave number will be [MH CET 2002]
A.	\[166\times {{10}^{3}}\] m?1
B.	\[16.6\times {{10}^{-1}}\] m?1
C.	\[1.66\times {{10}^{6}}\] m?1
D.	\[1.66\times {{10}^{7}}\] m?1
Answer» D. \[1.66\times {{10}^{7}}\] m?1

Discussion

711.	Assertion : Compression and rarefaction involve changes in density and pressure. Reason : When particles are compressed, density of medium increases and when they are rarefied, density of medium decreases.
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

712.	Assertion : Ocean waves hitting a beach are always found to be nearly normal to the shore. Reason : Ocean waves are longitudinal waves.
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

713.	What is the difference between soft and hard X-rays [MP PMT 2002; AIIMS 2002]
A.	Velocity
B.	Intensity
C.	Frequency
D.	Polarization
Answer» D. Polarization

Discussion

714.	In the following common emitter configuration an NPN transistor with current gain \[\beta =100\] is used. The output voltage of the amplifier will be
A.	\[10\,\,mV\]
B.	\[0.1\text{ }V\]
C.	\[1.0\text{ }V\]
D.	\[10\text{ }V\]
Answer» D. \[10\text{ }V\]

Discussion

715.	Two identical thin Plano convex lenses of refractive index n are silvered, one on the plane side and the other on the convex side. The ratio of their focal lengths is
A.	\[\frac{n}{n-1}\]
B.	\[\frac{n-1}{n}\]
C.	\[\frac{n+1}{n}\]
D.	\[n\]
Answer» B. \[\frac{n-1}{n}\]

Discussion

716.	Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added [MP PET 1999]
A.	The material obtained will be N-type germanium in which electrons and holes are equal in number
B.	The material obtained will be P-type germanium
C.	The material obtained will be N-type germanium which has more electrons than holes at room temperature
D.	The material obtained will be N-type germanium which has less electrons than holes at room temperature
Answer» D. The material obtained will be N-type germanium which has less electrons than holes at room temperature

Discussion

717.	The phenomena of total internal reflection is seen when angle of incidence is [RPMT 2001]
A.	\[{{90}^{o}}\]
B.	Greater than critical angle
C.	Equal to critical angle
D.	\[{{0}^{o}}\]
Answer» C. Equal to critical angle

Discussion

718.	A normally incident ray reflected at an angle of \[{{90}^{o}}\]. The value of critical angle is [RPMT 1996]
A.	\[{{45}^{o}}\]
B.	\[{{90}^{o}}\]
C.	\[{{65}^{o}}\]
D.	\[{{43.2}^{o}}\]
Answer» C. \[{{65}^{o}}\]

Discussion

719.	A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is \[\frac{4}{3}\] and the fish is 12 cm below the surface, the radius of this circle in cm is [NCERT 1980; KCET 2002; AIEEE 2005; CPMT 2005]
A.	\[36\sqrt{5}\]
B.	\[4\sqrt{5}\]
C.	\[36\sqrt{7}\]
D.	\[36/\sqrt{7}\]
Answer» E.

Discussion

720.	The radius of the Bohr orbit in the ground state of hydrogen atom is 0.5 Å. The radius of the orbit of the electron in the third excited state of \[H{{e}^{+}}\] will be [MP PMT 2000]
A.	8 Å
B.	4 Å
C.	0.5 Å
D.	0.25 Å
Answer» C. 0.5 Å

Discussion

721.	\[1\,eV\] is [SCRA 1986]
A.	Same as one joule
B.	\[1.6\times {{10}^{-19}}J\]
C.	\[1V\]
D.	\[1.6\times {{10}^{-19}}C\]
Answer» C. \[1V\]

Discussion

722.	Melting point of ice
A.	Increases with increasing pressure
B.	Decreases with increasing pressure
C.	Is independent of pressure
D.	Is proportional to pressure
Answer» C. Is independent of pressure

Discussion

723.	A one mole sample of an ideal gas is carried around the thermodynamic cycle shown in the figure. The cycle consists of three steps: (i) an isothermal expansion \[(a\to b),\] (ii) an isobaric compression \[(b\to c),\] and (iii) a constant volume increases in pressure \[(c\to a).\] If \[{{T}_{a}}=400K,\] \[{{P}_{a}}=4atm,\]and \[{{P}_{b}}={{P}_{c}},=1atm,\] the work done by the gas per cycle is
A.	211.6 J
B.	1158 J
C.	705.3 J
D.	2116 J
Answer» E.

Discussion

724.	A stretched wire 60 cm long is vibrating with its fundamental frequency of 256 Hz. If the length of the wire is decreased to 15 cm and the tension remains the same. Then the fundamental freuqency of the vibration of the wire will be
A.	1024
B.	572
C.	256
D.	64
Answer» B. 572

Discussion

725.	A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers 140°. What is the fall in temperature as registered by the Centigrade thermometer [CBSE PMT 1992; AIIMS 1998]
A.	30°
B.	40°
C.	60°
D.	80°
Answer» D. 80°

Discussion

726.	If the water falls from a dam into a turbine wheel 19.6 m below, then the velocity of water at the turbine is \[(g=9.8\,m/{{s}^{2}})\] [AIIMS 1998]
A.	9.8 m/s
B.	19.6 m/s
C.	39.2 m/s
D.	98.0 m/s
Answer» C. 39.2 m/s

Discussion

727.	Assertion : NOT gate is also called inverter circuit. Reason : NOT gate inverts the input order.
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

728.	Assertion : Zener diode works on a principle of breakdown voltage. Reason : Current increases suddenly after breakdown 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

729.	Assertion : In vacuum tubes (valves), vacuum is necessary for the movement of electrons between electrodes otherwise electrons collide with air particle and loses their energy. Reason : In semiconductors devices, external heating or vacuum is not required.
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

730.	A balloon with mass M is descending down with an acceleration a (a < g). What mass' of its contents must be removed so that it starts moving up with same acceleration a
A.	\[\frac{2M\left( g \right)}{a}\]
B.	\[\frac{M\left( g+a \right)}{g}\]
C.	\[\frac{Mg}{g+a}\]
D.	\[\frac{2Ma}{g+a}\]
Answer» E.

Discussion

731.	If radius of earth is R then the height ?h? at which value of ?g? becomes one-fourth is [BHU 2000]
A.	\[\frac{R}{4}\]
B.	\[\frac{3R}{4}\]
C.	R
D.	\[\frac{R}{8}\]
Answer» D. \[\frac{R}{8}\]

Discussion

732.	What is ratio of surface energy of 1 small drop and 1 large drop, if 1000 small drops combined to form 1 large drop [CPMT 1990]
A.	4.16736111111111
B.	1000 : 1
C.	10 : 1
D.	1 : 100
Answer» E.

Discussion

733.	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 [MP PMT 1996]
A.	500 seconds
B.	50 seconds
C.	5 seconds
D.	0.5 seconds
Answer» D. 0.5 seconds

Discussion

734.	Electrical conductivity of a semiconductor [MP PMT 1993, 2000; RPET 1996]
A.	Decreases with the rise in its temperature
B.	Increases with the rise in its temperature
C.	Does not change with the rise in its temperature
D.	First increases and then decreases with the rise in its temperature
Answer» C. Does not change with the rise in its temperature

Discussion

735.	Assertion : The resistivity of a semiconductor increases with temperature. Reason : The atoms of a semiconductor vibrate with larger amplitude at higher temperature there by increasing it's resistivity. [AIIMS 2003]
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

736.	Assertion : A transistor amplifier in common emitter configuration has a low input impedence. Reason : The base to emitter region is forward biased. [AIIMS 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

737.	Assertion : If the temperature of a semiconductor is increased then it's resistance decreases. Reason : The energy gap between conduction band and valence band is very small [AIIMS 1997]
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

738.	The amount of work done in an adiabatic expansion from temperature T to \[{{T}_{1}}\] is
A.	\[R(T-{{T}_{1}})\]
B.	\[\frac{R}{\gamma -1}(T-{{T}_{1}})\]
C.	RT
D.	\[R(T-{{T}_{1}})(\gamma -1)\]
Answer» C. RT

Discussion

739.	The speed of a wave in a certain medium is 960 m/s. If 3600 waves pass over a certain point of the medium in 1 minute, the wavelength is [MP PMT 2000]
A.	2 metres
B.	4 metres
C.	8 metres
D.	16 metres
Answer» E.

Discussion

740.	A mass m is suspended by means of two coiled spring which have the same length in unstretched condition as in figure. Their force constant are k1 and k2 respectively. When set into vertical vibrations, the period will be [MP PMT 2001]
A.	\[2\pi \sqrt{\left( \frac{m}{{{k}_{1}}{{k}_{2}}} \right)}\]
B.	\[2\pi \sqrt{m\left( \frac{{{k}_{1}}}{{{k}_{2}}} \right)}\]
C.	\[2\pi \sqrt{\left( \frac{m}{{{k}_{1}}-{{k}_{2}}} \right)}\]
D.	\[2\pi \sqrt{\left( \frac{m}{{{k}_{1}}+{{k}_{2}}} \right)}\]
Answer» E.

Discussion

741.	Two bodies M and N of equal masses are suspended from two separate massless springs of force constants k1 and k2 respectively. If the two bodies oscillate vertically such that their maximum velocities are equal, the ratio of the amplitude M to that of N is [IIT-JEE 1988; MP PET 1997, 2001; MP PMT 1997; BHU 1998; Pb. PMT 1998; MH CET 2000, 03; AIEEE 2003]
A.	\[\frac{{{k}_{1}}}{{{k}_{2}}}\]
B.	\[\sqrt{\frac{{{k}_{1}}}{{{k}_{2}}}}\]
C.	\[\frac{{{k}_{2}}}{{{k}_{1}}}\]
D.	\[\sqrt{\frac{{{k}_{2}}}{{{k}_{1}}}}\]
Answer» E.

Discussion

742.	A spring has a certain mass suspended from it and its period for vertical oscillation is T. The spring is now cut into two equal halves and the same mass is suspended from one of the halves. The period of vertical oscillation is now [MP PET 1995]
A.	\[\frac{T}{2}\]
B.	\[(3/2)k\]
C.	\[6k\]
D.	\[\sqrt{{{K}_{1}}}:\sqrt{{{K}_{2}}}\]
Answer» C. \[6k\]

Discussion

743.	The value of surface tension of a liquid at critical temperature is [AIIMS 1980]
A.	Zero
B.	Infinite
C.	Between 0 and \[\infty \]
D.	Cannot be determined
Answer» B. Infinite

Discussion

744.	Young's double slit experiment is made in a liquid. The \[{{10}^{th}}\] bright fringe lies in liquid where \[{{6}^{th}}\] dark fringe lies in vacuum. The refractive index of the liquid is approximately
A.	1.8
B.	1.5
C.	1.3
D.	1.6
Answer» B. 1.5

Discussion

745.	In frequency modulation [Kerala PMT 2005]
A.	The amplitude of modulated wave varies as frequency of carrier wave
B.	The frequency of modulated wave varies as amplitude of modulating wave
C.	The amplitude of modulated wave varies as amplitude of carrier wave
D.	The frequency of modulated wave varies as frequency of modulating wave
E.	(e) The frequency of modulated wave varies as frequency of carrier wave
Answer» C. The amplitude of modulated wave varies as amplitude of carrier wave

Discussion

746.	The electrical circuits used to get smooth d.c. output from a rectifier circuit is called [KCET 2000]
A.	Filter
B.	Amplifier
C.	Full wave rectifier
D.	Oscillator
Answer» C. Full wave rectifier

Discussion

747.	Two plane mirrors are inclined to each other at some angle. A ray of light incident at \[30{}^\circ \] on one, after reflection from the other retraces its path. The angle between the, mirrors is
A.	\[30{}^\circ \]
B.	\[45{}^\circ \]
C.	\[60{}^\circ \]
D.	\[90{}^\circ \]
Answer» B. \[45{}^\circ \]

Discussion

748.	Assertion : By roughening the surface of a glass sheet its transparency can be reduced. Reason : Glass sheet with rough surface absorbs more light. [AIIMS 2005]
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

749.	Assertion : The cloud in sky generally appear to be whitish. Reason : Diffraction due to cloud is efficient in equal measure at all wavelengths. [AIIMS 2005]
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

750.	Assertion : Diamond glitters brilliantly. Reason : Diamond does not absorb sunlight. [AIIMS 2005]
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

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

A string of 7 m length has a mass of 0.035 kg. If tension in the string is 60.5 N, then speed of a wave on the string is [CBSE PMT 2001]

In order to double the frequency of the fundamental note emitted by a stretched string, the length is reduced to \[\frac{3}{4}\]th of the original length and the tension is changed. The factor by which the tension is to be changed, is [EAMCET 2001]

Two perfectly identical wires are in unison. When the tension in one wire is increased by 1%, then on sounding them together 3 beats are heard in 2 sec. The initial frequency of each wire is : [Pb. PET 2002]

The first overtone of a stretched wire of given length is 320 Hz. The first harmonic is : [DPMT 2004]

A tuning fork of frequency 392 Hz, resonates with 50 cm length of a string under tension (T). If length of the string is decreased by 2%, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is [BHU 2004]

If \[\lambda \]=10Å, then it corresponds to [DCE 2000]

In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is [AFMC 1998; CPMT 2000; Pb. PET 2002]

Assertion : Separation of isotope is possible because of the difference in electron numbers of isotope. Reason : Isotope of an element can be separated by using a mass spectrometer. [AIIMS 1999]

Assertion : The velocity of sound increases with increase in humidity. Reason : Velocity of sound does not depend upon the medium.

If wavelength of a wave is \[\lambda =6000{AA}.\] Then wave number will be [MH CET 2002]

Assertion : Compression and rarefaction involve changes in density and pressure. Reason : When particles are compressed, density of medium increases and when they are rarefied, density of medium decreases.

Assertion : Ocean waves hitting a beach are always found to be nearly normal to the shore. Reason : Ocean waves are longitudinal waves.

What is the difference between soft and hard X-rays [MP PMT 2002; AIIMS 2002]

In the following common emitter configuration an NPN transistor with current gain \[\beta =100\] is used. The output voltage of the amplifier will be

Two identical thin Plano convex lenses of refractive index n are silvered, one on the plane side and the other on the convex side. The ratio of their focal lengths is

Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added [MP PET 1999]

The phenomena of total internal reflection is seen when angle of incidence is [RPMT 2001]

A normally incident ray reflected at an angle of \[{{90}^{o}}\]. The value of critical angle is [RPMT 1996]

A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is \[\frac{4}{3}\] and the fish is 12 cm below the surface, the radius of this circle in cm is [NCERT 1980; KCET 2002; AIEEE 2005; CPMT 2005]

The radius of the Bohr orbit in the ground state of hydrogen atom is 0.5 Å. The radius of the orbit of the electron in the third excited state of \[H{{e}^{+}}\] will be [MP PMT 2000]

\[1\,eV\] is [SCRA 1986]

Melting point of ice

A stretched wire 60 cm long is vibrating with its fundamental frequency of 256 Hz. If the length of the wire is decreased to 15 cm and the tension remains the same. Then the fundamental freuqency of the vibration of the wire will be

A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers 140°. What is the fall in temperature as registered by the Centigrade thermometer [CBSE PMT 1992; AIIMS 1998]

If the water falls from a dam into a turbine wheel 19.6 m below, then the velocity of water at the turbine is \[(g=9.8\,m/{{s}^{2}})\] [AIIMS 1998]

Assertion : NOT gate is also called inverter circuit. Reason : NOT gate inverts the input order.

Assertion : Zener diode works on a principle of breakdown voltage. Reason : Current increases suddenly after breakdown voltage.

Assertion : In vacuum tubes (valves), vacuum is necessary for the movement of electrons between electrodes otherwise electrons collide with air particle and loses their energy. Reason : In semiconductors devices, external heating or vacuum is not required.

A balloon with mass M is descending down with an acceleration a (a < g). What mass' of its contents must be removed so that it starts moving up with same acceleration a

If radius of earth is R then the height ?h? at which value of ?g? becomes one-fourth is [BHU 2000]

What is ratio of surface energy of 1 small drop and 1 large drop, if 1000 small drops combined to form 1 large drop [CPMT 1990]

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 [MP PMT 1996]

Electrical conductivity of a semiconductor [MP PMT 1993, 2000; RPET 1996]

Assertion : The resistivity of a semiconductor increases with temperature. Reason : The atoms of a semiconductor vibrate with larger amplitude at higher temperature there by increasing it's resistivity. [AIIMS 2003]

Assertion : A transistor amplifier in common emitter configuration has a low input impedence. Reason : The base to emitter region is forward biased. [AIIMS 2004]

Assertion : If the temperature of a semiconductor is increased then it's resistance decreases. Reason : The energy gap between conduction band and valence band is very small [AIIMS 1997]

The amount of work done in an adiabatic expansion from temperature T to \[{{T}_{1}}\] is

The speed of a wave in a certain medium is 960 m/s. If 3600 waves pass over a certain point of the medium in 1 minute, the wavelength is [MP PMT 2000]

A mass m is suspended by means of two coiled spring which have the same length in unstretched condition as in figure. Their force constant are k1 and k2 respectively. When set into vertical vibrations, the period will be [MP PMT 2001]

A spring has a certain mass suspended from it and its period for vertical oscillation is T. The spring is now cut into two equal halves and the same mass is suspended from one of the halves. The period of vertical oscillation is now [MP PET 1995]

The value of surface tension of a liquid at critical temperature is [AIIMS 1980]

Young's double slit experiment is made in a liquid. The \[{{10}^{th}}\] bright fringe lies in liquid where \[{{6}^{th}}\] dark fringe lies in vacuum. The refractive index of the liquid is approximately

In frequency modulation [Kerala PMT 2005]

The electrical circuits used to get smooth d.c. output from a rectifier circuit is called [KCET 2000]

Two plane mirrors are inclined to each other at some angle. A ray of light incident at \[30{}^\circ \] on one, after reflection from the other retraces its path. The angle between the, mirrors is

Assertion : By roughening the surface of a glass sheet its transparency can be reduced. Reason : Glass sheet with rough surface absorbs more light. [AIIMS 2005]

Assertion : The cloud in sky generally appear to be whitish. Reason : Diffraction due to cloud is efficient in equal measure at all wavelengths. [AIIMS 2005]

Assertion : Diamond glitters brilliantly. Reason : Diamond does not absorb sunlight. [AIIMS 2005]